Device and method for manufacturing carbonated spring and carbonic water, control method for gas density applied thereto, and membrane module

ABSTRACT

Hot water ( 12 ) in a bath ( 11 ) is pumped up by a suction pump ( 9 ) and introduced into a carbon dioxide gas dissolver ( 7 ) through solution flow rate adjusting means ( 14 ) and then, poured into the bath ( 11 ). Carbon dioxide gas supplied from a carbon dioxide gas cylinder ( 1 ) is introduced into the carbon dioxide gas dissolver ( 7 ) through gas flow rate adjusting means ( 5 ). At this time, the quantity of bubbles existing in artificial carbonated spring in a take-out pipe ( 15 ) is measured with a measuring device ( 13 ), and the solution flow rate adjusting means ( 14 ), gas flow rate adjusting means ( 5 ) and the like are controlled by means of a control device ( 16 ) using a relational expression between a preliminarily set quantity of bubbles and carbon dioxide concentration to obtain a desired concentration of carbon dioxide gas in carbonated spring. Because the carbon dioxide gas flow control means ( 5 ) is provided between the carbon dioxide gas dissolver ( 7 ) and a carbon dioxide gas supply source, carbonated spring of a high concentration can be always manufactured even if the pressure of supplied carbon dioxide gas changes or the permeating performance of a membrane changes.

TECHNICAL FIELD

[0001] The present invention relates to a device and method formanufacturing carbonated spring and carbonic water. More specifically,the present invention relates to a device and method for manufacturingcarbonated spring and carbonic water having a high concentration inorder to always obtain a predetermined carbonic acid concentrationeffectively. Further, the present invention relates to a method formeasuring the gas concentration of a gas dissolved solution obtained bydissolving gas into a liquid and a device for manufacturing thesolution. More particularly, the present invention relates to a methodfor controlling the gas concentration in the solution manufacturedcontinuously to a desired concentration and a device for manufacturing apreferable gas dissolved solution and a membrane module for dissolvinggas into the liquid effectively.

BACKGROUND ART

[0002] Solution in which gas is dissolved is used for various kinds ofapplication. If exemplifying carbon dioxide gas as a gas, weak carbonicwater having a low carbon dioxide gas concentration, carbonic beveragewhose carbon dioxide gas concentration is intensified under a highpressure, artificial carbonated spring in which carbon dioxide gas isdissolved in hot water, carbon dioxide dissolved solution used forindustrial purpose and the like have been widely used.

[0003] Generally, hot spring effects such as blood vessel expansioneffect gained in taking bath in hot water containing carbon dioxide gassuch as carbonated spring and difficulty of chilling after bath havebeen well known and utilized in public springs and the like using hotspring since before. The keeping warm effect of the carbonated springis, basically, considered to be because the physical environment isimproved by distal blood vessel expansion effect of contained carbondioxide gas. Further, carbon dioxide enters the skin so that capillarybeds are increased and expanded thereby improving circulation of bloodin the skin. Thus, it is considered that this has an effect in cure onregressive disease and distal circulation trouble. Further, a curativeeffect under a high concentration of about several hundreds mg/l to1,000 mg/l has been verified in recent years. For the reasons, chemicalsand devices capable of providing carbonic water for bath easily havebeen marketed.

[0004] To obtain such carbonated spring artificially, a chemical methodfor allowing carbonate to react with acid, a method by using combustiongas from a boiler, a device for blowing carbon dioxide gas directly intoa pipe having a throttle as disclosed in Japanese Patent ApplicationLaid-Open NO. 5-238928, a method by using a static mixer as a carbon gasdissolver as disclosed in Japanese Patent Application Publication Nos.7-114790 and 7-114791, and the like are available.

[0005] Recently, many methods for producing carbonated spring by using amembrane have been proposed. For example, Japanese Patent No. 2810694uses a hollow yarn membrane module incorporating plural porous hollowyarn membranes whose both ends are open and further, Japanese PatentNos. 3048499 and 3048501, Japanese Patent Application Laid-OpenNo.2001-293344 and the like have proposed methods of using a nonporoushollow yarn membrane as a hollow yarn membrane.

[0006] As a method for producing carbonated spring using a membrane, aso-called one-pass type in which carbonated spring is produced bypassing raw water through a carbon dioxide gas dissolver having amembrane module once and a so-called circulation type in which hot wateris circulated in a bath through a carbon dioxide gas dissolver using acirculation pump are available.

[0007] Meanwhile, the method by using the porous hollow yarn membranehas such a fear that the membrane turns hydrophilic due to a long termusage so that water leaks to the gas side to seal the membrane surface,thereby initial carbon dioxide gas adding ability is eliminated.Contrary to this, if the nonporous hollow yarn membrane is used, thenonporous membrane exists between the gas side and the liquid side, sothat no water may leak to the gas side despite a long term usage.However, there is a fear that because water vapor which is watermolecular passes, the passing water vapor is condensed on the gas side,thereby the condensed water (drain) seals the membrane surface.

[0008] Thus, according to the Japanese Patent Application Laid-Open Nos.7-313855 and 7-328403, a drain release valve is disposed on the gas sideand the valve is opened/closed periodically to discharge drain from thegas side. However, according to this method, the drain release needs tobe carried out frequently for a membrane in which the amount of passingvapor is large and thus, carbon dioxide gas charged on the gas sideneeds to be discharged into the atmosphere, and therefore, the amount ofconsumption of carbon dioxide gas is likely to be increased.

[0009] On the other hand, if the carbonated spring is produced accordingto the method by using the membrane, there is a disadvantage that thesame carbon concentration cannot be secured each time although thecarbonated spring having a high concentration can be obtained mosthighly effectively. Particularly, if the carbonated spring is produced anumber of times continuously on the same day, a phenomenon that thecarbonic acid concentration drops in the initial period of carbondioxide gas passage occurs.

[0010] According to the above-described methods, although flow rate andpressure are indicated for control of carbon dioxide gas, only the flowrate is controlled under the pressure control using a pressure controlvalve or the like which is used by being directly connected to a gascylinder as indicated in many of the embodiments. Thus, the flow rate ofthe carbon dioxide gas passing through the membrane differs between theinitial period of the passage and its stabilizing period. The reason whythe flow rate of the carbon dioxide gas changes is considered to be thatbecause the membrane is cooler than the water temperature in the initialperiod and the concentration of carbon dioxide gas in the membrane islow, the carbon dioxide is unlikely to pass through the membrane evenunder the same pressure. However, if carbonated spring having someappropriate concentration is produced, there is no any problem at thattime and not so much attention is paid to the accuracy.

[0011] However, in case of carbonated spring in the vicinity of a carbondioxide gas saturated concentration at 40° C., which is around 1200mg/l, it has been made evident that in terms of its curative effect, afurther remarkable effect can be expected and there is no way butchanging a though that everything is satisfied if carbonated springhaving an appropriate concentration is produced. Thus, a necessity ofproducing the carbonated spring with a high concentration and excellentreproducibility is generated. On the other hand, the above-mentionedcarbon dioxide gas dissolver has been modified frequently so thatimprovement of carbon dioxide gas dissolving efficiency has been triedgradually. However, a further improvement in the dissolving efficiencyhas been demanded. Particularly in a full-body bathing device which usesa large amount of carbon dioxide gas, the improvement in the dissolvingefficiency is important.

[0012] Even a method using pressure control is capable of producingcarbonated spring having a high concentration if an operation method byproviding with an allowance is used, for example, by setting a slightlyexcessively high pressure or increasing the operation time in case of acirculation type. However, if such a method is applied, carbon dioxidegas is consumed wastefully, which is not preferable.

[0013] Further, in case of application for hospitals, a method ofproducing high-concentration carbonated spring in as short a time aspossible has been demanded in order to care as many patients aspossible. However, the circulation type has such a disadvantage that thetime for producing the high-concentration carbonated spring is prolongedbecause no sufficient flow rate is secured in the initial period.

[0014] On the other hand, the method for producing carbonated springwith an excellent reproducibility by using the one-pass type has beendescribed in Japanese Patent Application Laid-Open No. 10-277121.According to this method, the concentration of carbon dioxide gas in theproduced carbonated spring is measured and by feeding back theconcentration, the quantity of carbon dioxide gas supplied iscontrolled. For the reason, it takes a long time to reach a targetcarbon dioxide gas concentration. Further, this method has such adisadvantage that if alkali degree of raw water changes, no excellentreproduction can be attained.

[0015] Examples of the method for measuring the concentration of gas ina gas dissolved solution include a method for measuring the gasconcentration by using a gas concentration measuring device of ionelectrode type, a method for measuring the gas concentration bymeasuring pH after preliminarily measured alkaline degrees areprogrammed, a method for measuring the gas concentrationelectrochemically after the pH value of a solution is adjusted by addingchemical to the solution, a method for measuring the gas concentrationaccording to thermal conductivity of gas discharged by adding chemicalto a solution, a method for measuring the gas concentration according toinfrared ray absorption ratio of a solution, a method for measuring thegas concentration by detecting the pressure of gas discharged from asolution when ultrasonic wave is applied thereto (Japanese PatentApplication Laid-Open No. 5-296904) and the like.

[0016] However, according to the above-described gas measuring method,since its operation is very complicated and upon usage, it takes a largenumber of time and labor, the concentration of gas in a solutionproduced continuously from a dissolver cannot be measured on time.

[0017] Hereinafter, artificial carbonated spring will be described as anexample of solution. Generally, the artificial carbonated spring isproduced as artificial carbonated spring by dissolving carbon dioxidegas of a predetermined concentration in hot water. Because it isconsidered that the artificial carbonated spring has an excellent effectupon distal blood circulation trouble by its strong blood vesselexpanding action, it has been widely used for cure and hot spring cure.Although carbonated spring spouted naturally is used up to now,currently, the artificial carbonated spring cure has been widely used asone internal medicine cure due to development of the excellentartificial spring production method.

[0018] From the clinical research result in the artificial carbonatedspring cure, it has been made evident that the effective concentrationof carbon dioxide gas usable for cure becomes max from 1,000 mg/l toabout 1,400 mg/l. Additionally, it has been indicated thatresponsibility to the carbon dioxide gas concentration differs dependingon the degree of seriousness of disease and continuation period of cure.In actual artificial carbonated spring cure, it is necessary to set anappropriate concentration of carbon dioxide gas corresponding to apatient.

[0019] Thus, if the artificial carbonated spring is used for cure, theconcentration of carbon dioxide gas dissolved in a solution is animportant factor. The artificial carbonated spring of a predeterminedconcentration produced continuously with a dissolver requests to takebath just after it is stored in a storage bath. If it takes long formeasurement of the concentration of gas in the artificial carbonatedspring, carbon dioxide gas in the storage bath is emitted into theatmosphere so that the concentration of gas in the artificial carbonatedspring drops. If a patient takes a bath in this condition, he/she cannottake bath under a desired carbon dioxide gas concentration so that thecurative effect by the artificial carbonated spring cannot be expected.Further, when necessity of measuring the gas concentration a number oftimes repeatedly exists, it comes that the temperature of hot wateritself drops.

[0020] Particularly, if the carbon dioxide gas concentration is measuredaccording to the ion electrode type method, it takes several minutesuntil a measuring result is obtained, so that the measuring resultcannot be obtained in a short time because several minutes is alwaysneeded for each measurement. Further, according to the method ofmeasuring the carbon dioxide gas concentration by measuring pH after thealkaline degree is programmed preliminarily, it is necessary to measurean alkaline degree preliminarily in each case, the alkaline degreedifferent depending on water quality. Moreover, if other ion or salt ismixed, the alkaline degree needs to be measured again, and to obtain aresponse result of the pH measurement, it takes some time. Thus, thecarbon dioxide gas concentration cannot be measured in line at the sametime when the artificial carbonated spring is produced.

[0021] On the other hand, examples of the method for producing theartificial spring include a method of dissolving bubbles of carbondioxide gas generated by chemical reaction in hot water (Japanese PatentApplication Laid-Open No. 2-270158), a method of filling hot water in apressure tank with carbon dioxide gas under a high pressure, a method ofmixing carbon dioxide gas with hot water forcibly by an agitator calledstatic mixer in a diffuser provided halfway of a hot water conduit(Japanese Patent Application Laid-Open No. 63-242257), a method by usinga multi-layer composite hollow yarn membrane dissolver (“Carbonic WaterProducing Device MRE-SPA” made by Mitsubishi Rayon Engineering Co.,Ltd.), and the like.

[0022] The methods by using the static mixer or multi-layer compositehollow yarn membrane dissolver are suitable for production of a largeamount of the artificial carbonated spring continuously and by passinghot water through the carbon dioxide gas dissolver repeatedly by meansof the circulation path, the concentration of the carbon gas can beraised gradually up to a predetermined concentration.

[0023] In case of producing artificial carbonated spring continuously,artificial carbonated spring having a predetermined carbon dioxide gasconcentration can be produced by combining the carbon dioxide gasconcentration measuring means with the artificial carbonated springmanufacturing method. However, the case of producing the artificialcarbonated spring continuously in line has a problem in responsevelocity in the method for measuring the concentration of carbonatedoxide gas. Although measurement based on the ion electrode method is ageneral method as a method for measuring the concentration of carbondioxide gas in water, its response velocity is slow and particularly, asolution whose carbon gas dioxide concentration is 1000 to 1400 mg/l,required for the artificial carbonated spring takes long hours for theion electrode to be balanced. Further, because gas bubbles adhere to theion electrode thereby disabling accurate measurement, the measurement inline and on time is difficult to achieve.

[0024] Further, if the membrane is stained gradually each time of use,carbon dioxide gas becomes hard to flow, so that a deflection occurs inthe relation between a carbon dioxide gas pressure and a flow ratecreated first, thereby disabling a right flow control. Although it maybe possible to achieve the right control if the relation betweenpressure and flow rate is investigated each time of use, the operationfor that purpose is very troublesome.

[0025] An object of the present invention is to solve theabove-described problems and more particularly to provide a device andmethod for manufacturing carbonated spring and carbonic water having ahigh concentration effectively, and a device and method formanufacturing carbonated spring and carbonic water capable of alwaysobtaining a constant carbonic acid concentration despite changes in themembrane permeating performance. Another object of the present inventionis to provide a membrane module which allows soluble gas to be dissolvedinto liquid effectively, a method for measuring the concentration of gasdissolved in a solution produced continuously in line and on time, and adevice for manufacturing a dissolved solution having a desired gasconcentration effectively.

DISCLOSURE OF THE INVENTION

[0026] The most basic configuration of the present invention is a devicefor manufacturing carbonated spring, comprising: a membrane module whichdissolves carbon dioxide gas into hot water through a membrane; meansfor supplying hot water to the membrane module; and means for supplyingcarbon dioxide gas to the membrane module, wherein a flow control valvewhich maintains the flow rate of carbon dioxide gas constant is providedbetween the means for supplying carbon dioxide gas and the membranemodule.

[0027] Preferably, the flow control valve is a mass-flow-rate type flowcontrol valve, a flow meter is provided between the flow control valveand the means for supplying carbon dioxide gas and further, a pressurecontrol valve for maintaining gas pressure constant is provided betweenthe means for supplying carbon dioxide gas and the flow control valve.Adopting such configurations enables the flow rate of carbon dioxide gasto be adjusted more accurately.

[0028] Further, preferably, the membrane is hollow yarn and the hollowyarn membrane is a three-layered composite hollow yarn membrane in whichboth sides of a thin nonporous gas permeating layer are sandwiched byporous layers. If adopting the composite hollow yarn membrane, carbondioxide gas can be dissolved into hot water or water efficiently.

[0029] In addition, the second basic configuration of the presentinvention is a method for manufacturing carbonated spring, wherein, whencarbonated spring is manufactured by dissolving carbon dioxide gas intohot water through a membrane, the flow rate of carbon dioxide gas iscontrolled to be constant. Preferably, as described previously, thecarbon dioxide gas flow rate is controlled to be constant by the flowcontrol valve. Preferably, the mass flow rate type flow control valve, ahollow yarn membrane as the membrane and particularly, a three-layeredcomposite hollow yarn membrane in which both sides of a thin nonporousgas permeating layer are sandwiched by porous layers are used. Further,when carbonated spring is manufactured using the circulation typesystem, the ratio between the flow rate of a circulation pump and theflow rate of carbon dioxide gas is preferred to be in a range of 2 to20.

[0030] Other basic configuration of the present invention is a devicefor manufacturing carbonated spring comprising: a carbon dioxide gassupply port; a carbon dioxide gas dissolver which communicates with thecarbon dioxide gas supply port; a water bath; a circulation pump forfeeding water in the water bath into the carbon dioxide gas dissolverand returning the fed water into the water bath; and carbon dioxide gassupply control means for changing the carbon dioxide gas supply velocityduring dissolving of carbon dioxide gas. Still other basic configurationof the present invention is a method for manufacturing carbonatedspring, wherein, when water in a water bath is circulated by acirculation pump through a carbon dioxide gas dissolver while carbondioxide gas is supplied into the carbon dioxide gas dissolver so as todissolve carbon dioxide gas into the water bath to raise the carbondioxide gas concentration of water in the water bath gradually, thecarbon dioxide gas supply velocity is retarded in the latter half periodof the carbon dioxide gas dissolving time as compared with the formerhalf period thereof. According to this manufacturing method, the carbondioxide gas concentration of water in the water bath after dissolving ofcarbon dioxide gas ends is preferred to be 1000 mg/l or more. By settingthe carbon dioxide gas concentration to a high concentration, bloodcirculation in the skin becomes easy to improve due to distal bloodvessel expansion action by the contained carbon dioxide gas andincrease/expansion of capillary beds by invasion of carbon dioxide gasthrough the skin.

[0031] Still other configuration of the present invention is a devicefor manufacturing a gas dissolved solution for carbonated spring,comprising: a carbon dioxide gas supply port; a carbon dioxide gasdissolver which communicates with the carbon dioxide gas supply port; awater bath; a circulation pump for feeding water in the water bath intothe carbon dioxide gas dissolver and returning the fed water into thewater bath; and carbon dioxide gas supply control means for changing thecarbon dioxide gas supply velocity during dissolving of carbon dioxidegas.

[0032] Preferably, when carbonated spring is manufactured by dissolvingcarbon dioxide gas into hot water through a membrane, the carbon dioxidegas flow rate is controlled to be constant. Preferably, a mass flow ratetype flow control valve is used as the flow control valve, a hollow yarnmembrane is used as the membrane, and particularly, a three-layeredcomposite hollow yarn membrane in which both sides of a thin nonporousgas permeating layer are sandwiched by porous layers is used. Further,the latter half of carbon dioxide gas dissolving time is preferred to belonger than the former half of carbon dioxide gas dissolving time. Thecarbon dioxide gas supply velocity just before dissolving of carbondioxide gas ends is preferred to be 50% or less with respect to thesupply velocity when dissolving of carbon dioxide gas starts.Consequently, carbonated spring having a high concentration can bemanufactured effectively.

[0033] In order to control the carbon dioxide gas supply velocity, it ispermissible to provide plural carbon dioxide gas supply velocity controlmeans in parallel. In this case, the carbon dioxide gas supply velocitycontrol means may be set to different supply velocities and then,changed over in order from the carbon dioxide gas supply velocitycontrol means having the highest setting of the carbon dioxide gassupply velocity. To change over the carbon dioxide gas supply velocity,it is desirable to use an electromagnetic valve and change over in orderunder electronic control.

[0034] Further, to control the carbon dioxide gas supply velocity,preferably, the flow control valve is used.

[0035] As described above, the flow control valve is preferred to be amass flow rate type flow control valve. Preferably, a flow meter isprovided between the flow control valve and the means for supplyingcarbon dioxide gas and a pressure control valve for maintaining gaspressure constant is provided between the means for supplying carbondioxide gas and the flow control valve. With these structures, the flowrate of carbon dioxide gas can be adjusted accurately.

[0036] Generally, as the flow control valve, there are a type affectingthe secondary pressure (outlet side pressure) such as an ordinaryorifice and needle valve and a type not affecting the secondarypressure. In case of the type affecting the secondary pressure, as thepressure of the secondary side increases, that is, a difference to theprimary pressure decreases, the flow rate is reduced. At this time, thevalve opening degree (CV value) and pressure are generally in afollowing relation.

[0037] Assuming that P₁ is a primary side absolute pressure (MPa), P₂ isa secondary side absolute pressure (MPa), Q is a flow rate (m³/h), and ρis a specific weight (assuming air to be 1), when P₂>(P₁/2),

CV=Q/4170×(ρ(273+t)/(P ₁ −P ₂)P ₂)^(1/2)

[0038] When P₂≦(P₁/2), the secondary pressure is not affected.

[0039] On the other hand, the mass flow control valve does not affectthe secondary pressure.

[0040] According to Japanese Patent Application Laid-Open NO. 58-139730,when the pressure is constant, carbon dioxide gas is fed, that is,because the secondary pressure is constant, the mass flow control valveis not required.

[0041] Contrary to this, preferably the mass flow control valve isadopted because the present invention utilizes the membrane module inwhich the secondary pressure changes depending on changes in state. As awell known mass flow control valve, there are an electronic valve andneedle valve. Although according to the present invention, the needlevalve type mass flow control valve is preferably used, it is permissibleto use the electronic type.

[0042] The mass flow control valve of the needle valve type adjusts theflow rate with a needle valve and is provided with a pressure adjustingvalve or the like whose opening degree is constant to the same mass flowrate so that the pressure at a valve outlet becomes constant, providedat the rear portion thereof. Consequently, the secondary pressure(outlet pressure) is always kept constant. Because the secondarypressure turns constant when the primary pressure (intake pressure) isconstant, the valve is called constant differential pressure adjustingvalve. Although the ordinary needle valve affects the secondarypressure, this mass flow control valve can adjust the mass flow rate toconstant even if the load pressure on the secondary side (outlet side)changes.

[0043] On the other hand, in the electronic mass flow control valve,resistors each having a large resistance temperature coefficient arewound around a capillary tube which is a sensor portion at its upstreamand downstream sides and by supplying a current to this, the tworesistors are heated. At this time, if no fluid flows through thecapillary tube, the upstream and downstream sides are balanced with thesame temperature. If fluid begins to flow in this state, the temperaturedistribution changes, so that the upstream side is deprived of heat byfluid while the downstream side is supplied with heat deprived from theupstream side. That is, there is generated a difference in temperaturebetween the upstream and downstream sides.

[0044] If attention is paid to that this temperature difference is in apredetermined functional relationship with the mass flow rate of fluidand a change of each resistance is fetched out as an electric signal andthen, amplified and corrected, a thermal type mass flow rate metercapable of measuring the mass flow rate functions under a certaincondition. This is an electronic type mass flow rate meter (mass flowmeter).

[0045] In the mass flow control valve (mass flow controller), a valveopening degree is controlled by a high-speed, high-resolution piezo orsolenoid actuator under comparative control with a flow rate settingsignal from outside based on a signal of mass flow rate outputted fromthe sensor portion. Consequently, a stabilized mass flow control isenabled hardly affected by changes in various conditions such astemperature and pressure.

[0046] According to the present invention, in the gas permeationmembrane preferable for carbon dioxide gas, preferably, its carbondioxide gas permeating amount at 25° C. is 1×10⁻³ to 1 m³/m²·hr·0.1 MPaand its vapor permeating amount at 25° C. is 1×10³ g/m² hr 0.1 MPa orless. Further, it is preferable to use a membrane module composed ofthese gas permeation membranes. If the gas permeation membrane is anonporous membrane having no Knudsen flow, the membrane gets wet so thatno water permeates to the gas supply side, which is preferable. If themembrane density of the membrane module is in a range of 2000 to 7000m²/m³, carbon dioxide gas can be dissolved effectively, which ispreferable.

[0047] It is preferable that the gas permeation membrane is a hollowyarn membrane, because the membrane area per volume can be raised.Although this hollow yarn may be composed of hollow yarn membrane formedof mere porous membrane, if the hollow yarn membrane is a three-layeredcomposite hollow yarn membrane in which both sides of a thin nonporousmembrane are sandwiched by porous membranes, carbon dioxide gas can bedissolved into hot water efficiently, which is preferable. If thethickness of the nonporous membrane is 0.1 to 500 μm, an appropriatestrength is possessed while carbon dioxide gas permeating performanceand vapor permeating performance are satisfied, which is preferable. Todissolve carbon dioxide gas using the carbon dioxide gas adding membranemodule, it is preferable to heat water to 30° C. to 50° C. preliminarilyand then dissolve it. Further, the carbon dioxide gas dissolver may be astatic mixer.

[0048] Moreover, to manufacture the above-described high concentrationcarbonated spring or carbonic water of 1000 mg/l or more, the method formeasuring the gas concentration in a dissolved solution which is anotheraspect of the present invention can be adopted. This is a gasconcentration measuring method developed by the inventor of the presentinvention, and applies the fact that when the flow rate of solutionpassing the gas dissolver and the supply flow rate of gas supplied tothe same gas dissolver are kept constant, there exists a certaincorrelation between the quantity of bubbles of undissolved gas existingin the take-out pipe from the gas dissolver and the gas concentration inthe dissolved solution introduced from the gas dissolver. Consequently,the gas concentration in the dissolved solution manufacturedcontinuously can be measured in line and on time. In the meantime, thegas concentration measuring method of the present invention is notrestricted to measurement of the gas concentration in the carbon dioxidegas solution only, but naturally may be applied to measurement of gasconcentration of other various kinds of soluble gases.

[0049] The basic configuration exists in a method for measuring a gasconcentration in a dissolved solution, comprising introducing solutionand gas of each specified flow rate into a gas dissolver, measuring thequantity of bubbles existing in a take-out pipe from the gas dissolverand measuring the gas concentration of a dissolved solution dischargedfrom the take-out pipe according to the quantity of the bubbles.

[0050] By introducing a specified amount of solution into the gasdissolver and a specified amount of gas, a dissolved solution after gasis dissolved into solution in the gas dissolver and gas not dissolved insolution, that is, gas mixed in the dissolved solution in the form ofbubbles is discharged through the take-out pipe from the gas dissolver.The quantity of bubbles of undissolved gas existing in the take-out pipeis measured continuously in line and on time so as to measure the gasconcentration in the dissolved solution introduced out from the gasdissolver continuously. As the quantity of gas introduced into the gasdissolver, it is desirable to introduce a quantity not less than thesaturated dissolved amount of the quantity of the introduced solutioninto the gas dissolver.

[0051] When obtaining a dissolved solution having a target gasconcentration by adding gas to dissolved solution of any concentrationthrough multiple stages, the quantity of gas which can be added in anext stage is decreased as the gas concentration of an initial dissolvedsolution is higher. Moreover, to maintain the flow rate of solutionpassing the gas dissolver and the supply flow rate of gas supplied tothe same gas dissolver, the quantity of bubbles of undissolved gasexisting in the take-out pipe from the gas dissolver and the gasconcentration in the dissolved solution introduced out from the gasdissolver have a specific correlation. Using this fact, the gasconcentration in the dissolved solution can be measured on time duringcontinuous manufacturing of the dissolved solution by measuring thequantity of bubbles in the dissolved solution in the take-out pipeaccording to a relational expression, which indicates the relationbetween the quantity of bubbles in the dissolved solution existing inthe take-out pipe and the gas concentration of the dissolved solutionand is obtained under various conditions in terms of the dissolvingcapacity of a gas dissolver, the introduction amount of solution and theflow rate of introduced gas.

[0052] When the dissolved solution is artificial carbonated spring, thegas concentration of the artificial carbonated spring manufactured bythe gas dissolver can be measured continuously in line and on timeeffectively from the quantity of bubbles in the take-out pipe duringmanufacturing of the artificial carbonated spring.

[0053] In addition to the above-described configuration, the quantity ofthe bubbles is preferred to be computed according to the damping rate ofultrasonic wave passing the take-out pipe using an ultrasonic wavetransmitter and an ultrasonic wave receiver disposed across the take-outpipe. As regards measuring of bubbles of gas in the dissolved solution,the quantity of bubbles is computed according to a damping rate(=(strength of ultrasonic wave signal received by ultrasonic wavereceiver)/(strength of ultrasonic wave signal transmitted fromultrasonic wave transmitter): %) of the strength of an ultrasonic wavesignal received by the ultrasonic wave receiver disposed in the take-outpipe after the ultrasonic wave signals dispatched from the ultrasonicwave transmitter disposed in the introduction pipe are passed throughthe dissolved solution in the take-out pipe.

[0054] The quantity of bubbles can be measured by causing the ultrasonicwave signal to pass through the take-out pipe in which the quantity ofbubbles of gas in the dissolved solution and the solution coexist. Thatis, the damping of the ultrasonic wave signal measured by the ultrasonicwave receiver is minimized (the damping rate is maximized) because theultrasonic wave signal dispatched from the ultrasonic wave transmitterpasses only the solution when no gas bubbles exist in the solution (whenthe supply amount of gas is 0 or gas introduced into the gas dissolveris dissolved 100% in the solution because the gas supply velocity to theflow velocity of the solution is small).

[0055] Because the conductivity of ultrasonic wave is different betweensolution and bubble, the damping of the ultrasonic wave signal increasesas more bubbles are mixed in the solution and when the solubility in thegas dissolver for use reaches 0, the damping of the ultrasonic wavesignal measured by the ultrasonic wave receiver is maximized (thedamping rate is minimized). Because the change in the damping rate ofthe ultrasonic wave signal is inherent of a gas dissolver, it ispossible to obtain a relational expression to a gas dissolver for use bymeasuring the damping rate of the ultrasonic wave signal and a measuredvalue of the gas concentration in the solution.

[0056] Particularly, because when the artificial carbonated spring isadopted as the solution, there is a tendency that the damping ratedecreases rapidly from the saturated concentration of carbon dioxide gasin the artificial carbonated spring, the change in the damping rate islarge in the vicinity of 1000 to 1400 mg/l which is an effective carbondioxide gas concentration as the artificial carbonated spring, so thatthe carbon dioxide gas concentration in the effective carbon dioxide gasconcentration range can be measured easily according to the quantity ofbubbles.

[0057] According to the present invention, preferably, the gasconcentration is specified according to the quantity of the measuredquantity of bubbles using the relational expression between the quantityof bubbles and gas concentration measured under a condition that thesolution flow rate and gas flow rate are constant. Here, the inventor ofthe present invention has recognized first that there exists a specifiedcorrelation between the quantity of bubbles in undissolved gas existingin the take-out pipe from the gas dissolver and the gas concentration inthe dissolved solution taken out from the gas dissolver or taken intothe gas dissolver by maintaining the flow rate of solution passing thegas dissolver and the supply amount of gas supplied to the same gasdissolver and this recognition is applied to the present invention.

[0058] That is, this specification can be carried out according to therelational expression by measuring the damping rate of the ultrasonicwave signal and the measured value of the gas concentration for thestate of solution to be introduced to the gas dissolver and the state ofgas. The states of the solution and gas can be set up depending onphysical condition (for example, flow rate for introduction, pressure,temperature, viscosity and the like). Because the relational expressionbetween the damping rate of the ultrasonic wave signal and the measuredvalue of the gas concentration differs depending on the physicalconditions of the solution and gas, it is desirable to keep the aboverelational expression under a condition for carrying out normaldissolving work.

[0059] Because the above-described relational expression differsdepending on the dissolving capacity of the gas dissolver, thetemperature, pressure and the like at the time of dissolving, it isnecessary to set up these conditions depending on the condition foractually manufacturing the dissolved solution to obtain the aboverelational expression based on the same condition.

[0060] Particularly, in case where the artificial carbonated spring isemployed as the dissolved solution, it is desirable to obtain theaforementioned relational expression under the condition that theintroduction flow rates of the artificial carbonated spring or hot waterand the introduction flow rate of carbon dioxide gas are kept at adesired flow rate at a temperature suitable for taking bath as thetemperature of hot water of artificial carbonated spring. The gasconcentration measuring method of the present invention is capable ofobtaining a preferable result if the gas dissolved solution isartificial carbonated spring. In manufacturing, for example, artificialcarbonated spring using carbon dioxide gas as its gas, the gasconcentration in the artificial carbonated spring being manufactured ismeasured based on the quantity of bubbles of carbon dioxide gas in thetake-out pipe discharged from the gas dissolver.

[0061] Thus, the gas concentration of the artificial carbonated springmanufactured by the gas dissolver can be measured continuously on timeeffectively according to the quantity of bubbles in the take-out pipeduring manufacturing of the artificial carbonated spring. Further, bymaking the bast of a tendency that the damping rate of the ultrasonicwave signal decreases rapidly from the vicinity of the saturatedconcentration of the carbon dioxide gas of the artificial carbonatedspring, the carbon dioxide gas concentration in the vicinity of 1000 to1400 mg/l, which is an effective carbon dioxide gas concentration as theartificial carbonated spring, can be detected or measured easily.

[0062] At a temperature suitable for taking bath in the artificialcarbonated spring, an relational expression between the quantity ofbubbles of carbon dioxide gas in the artificial carbonated spring takenout from the gas dissolver and the gas concentration of the artificialcarbonated spring is obtained preliminarily with the flow rate of theartificial carbonated spring or hot water introduced into the gasdissolver and the introduction flow rate of carbon dioxide gas set todesired specific flow rates. Then, the carbon dioxide gas concentrationof the artificial carbonated spring can be obtained in line and on timeduring manufacturing of the artificial carbonated spring.

[0063] According to still another aspect of the present invention, thegas concentration measuring method is achieved by a device formanufacturing a gas dissolved solution, comprising: a gas supply sourcehaving gas flow rate adjusting means; a gas dissolver in which gas andsolution are to be introduced from the gas supply source; solution flowrate adjusting means for controlling the flow rate of the solutionintroduced into the gas dissolver to be constant; and a take-out pipefor taking out the solution from the gas dissolver, the manufacturingdevice further comprising: a measuring device for measuring the quantityof gas bubbles existing in the take-out pipe; and a control device forcomputing the gas concentration of the dissolved solution based on arelational expression between the quantity of bubbles and gasconcentration measured preliminarily under a condition that the solutionflow rate and gas flow rate are constant and a measured value from themeasuring device and controlling the gas flow rate adjusting meansand/or the solution flow rate adjusting means based on the computationresult, securely and accurately.

[0064] According to the present invention, the gas concentration of adissolved solution is computed according to the quantity of gas bubblesexisting in the take-out pipe under measurement using the relationalexpression between the quantity of bubbles and gas concentrationobtained by preliminary measurement. Then, a dissolved solution having adesired gas concentration can be manufactured by controlling the gasflow rate adjusting means and/or the solution flow rate adjusting meansdepending on the computed gas concentration of the dissolved solution.

[0065] As regards control on the gas flow rate adjusting means and/orthe solution flow rate adjusting means, the introduction from the gasflow rate adjusting means and solution flow rate adjusting means intothe gas dissolver can be stopped when the gas concentration of thedissolved solution computed by the control device reaches a desired gasconcentration. Further, the gas concentration in the dissolved solutioncan be controlled based on the relational expression at changed flowrates in the gas flow and solution flow.

[0066] In this case, a number of the relational expressions between thegas flow rate and solution flow rate, which can be changed over inadvance, are prepared preliminarily and then, the gas flow rate andsolution flow rate optimum for a desired gas concentration are computedfrom the gas concentration computed from the quantity of bubbles in thesolution. Then, the gas flow rate adjusting means and solution flow rateadjusting means are controlled so as to reach the gas flow rate andsolution flow rate on the relational expression which is preliminarilymeasured and is the nearest the above computation result.

[0067] The measuring device is preferred to be composed of theultrasonic wave transmitter and ultrasonic wave receiver disposed acrossthe take-out pipe. By using the gas dissolved solution manufacturingdevice having such a configuration, the above-described operation andeffect can be obtained.

[0068] The gas dissolver may be constituted of a static mixer. Becausethe static mixer is a gas dissolver capable of introducing a specificamount of solution and soluble gas continuously from viewpoint of itsstructure and has a relatively high dissolving efficiency, it isadvantageous to adopt this as a dissolver. Particularly, because thestatic mixer is a gas dissolver capable of introducing a specifiedamount of hot water and carbon dioxide gas continuously and easily uponmanufacturing of the artificial carbonated spring and has a highdissolving efficiency for carbon dioxide gas, it is advantageous as agas dissolver for manufacturing the artificial carbonated spring.

[0069] Preferably, the gas dissolver is a hollow yarn membrane typedissolver. The hollow yarn membrane type dissolver allows gas to bedissolved in solution to be supplied at a stable flow rate and secures ahigh dissolving efficiency, so that gas can be dissolved in solution ina wider concentration range.

[0070] In the hollow yarn membrane type dissolver, solution is passed ona contact portion on the surface of the hollow yarn membrane and throughone side of the hollow portion while gas is passed through the otherside, so that gas is dissolved in solution using the action as a gasexchange membrane in the hollow yarn membrane. At the time of dissolvinggas, it is preferable to adjust the gas pressure and solution pressureto a pressure capable of obtaining a dissolved solution not less thanthe saturated gas concentration by adjusting the gas pressure adjustingunit and solution pressure adjusting unit connected to the hollow yarnmembrane type dissolver.

[0071] Particularly, its dissolving efficiency is relatively high in aconcentration region of 1000 mg/l or more necessary for the artificialcarbonated spring for manufacturing of the artificial carbonated spring,the relational expression between the quantity of bubbles and the carbondioxide gas concentration is maintained excellently and it is capable ofdetecting the carbon dioxide gas concentration in a carbon dioxide gasconcentration region effective for the artificial carbonated spring at ahigh accuracy.

[0072] Preferably, it further comprises a storage bath for storingdissolved solution discharged from the take-out pipe, wherein liquid inthe storage bath is circulated to the gas dissolver through the solutionflow rate adjusting means. A desired amount of gas can be dissolved inthe dissolved solution from the gas dissolver by circulating thesolution in the storage bath through the solution flow rate adjustingmeans. Thus, the dissolved solution in the storage bath is introducedfrom the storage bath into the gas dissolver through a liquid feedingpump or the like and gas is added gradually to the dissolved solution soas to raise the gas concentration.

[0073] By measuring the gas concentration of the dissolved solutionpassing the gas dissolver, gas can be added until the gas concentrationof the dissolve solution in the storage bath reaches a target gasconcentration, so that a dissolved solution of a desired gasconcentration can be manufactured. At this time, if a relationalexpression between the damping rate of the ultrasonic wave signal andthe gas concentration of the solution introduced into the dissolverinstead of the gas concentration of the solution taken out from thedissolver is obtained preliminarily for a gas dissolver for use, the gasconcentration of the solution in the storage bath can be detected.

[0074] Even if new solution is added to the storage bath, a dissolvedsolution of a desired gas concentration can be manufactured bycirculating the dissolved solution into the gas dissolver. Thus, adissolved solution of a desired gas concentration can be always held ata specified amount in the storage bath.

[0075] On the other hand, a target gas concentration can be manufacturedcontinuously by changing the ratio between the flow rate of solution tobe introduced into the gas dissolver and the gas supply flow rate whilemeasuring the gas concentration in the dissolved solution which passesthrough the gas dissolver, the solution being introduced directly intothe storage bath through a supply port such a faucet.

[0076] Upon manufacturing of the artificial carbonated spring, theartificial carbonated spring having a desired carbon dioxide gasconcentration can be manufactured easily by circulating the artificialcarbonated spring to the gas dissolver and further a desired amount ofthe artificial carbonated spring can be manufactured continuously whilemeasuring the carbon dioxide gas concentration.

BRIEF DESCRIPTION OF DRAWINGS

[0077]FIG. 1 is a diagram showing a schematic entire configuration of acirculation type device preferably used for the present invention;

[0078]FIG. 2 is a diagram showing a schematic entire configuration ofanother circulation type device preferably used for the presentinvention;

[0079]FIG. 3 is a diagram showing a schematic entire configuration of aone-pass type device preferably used for the present invention;

[0080]FIG. 4 is a schematic sectional view showing an example of acarbon dioxide gas adding membrane module of the present invention;

[0081]FIG. 5 is a schematic view showing an example of a hollow yarnmembrane for use in the present invention;

[0082]FIG. 6 is a diagram showing a configuration of a device formanufacturing artificial carbonated spring according to an embodiment ofthe present invention;

[0083]FIG. 7 is a relational diagram between damping rate and gasconcentration; and

[0084]FIG. 8 is a block diagram of signal processing.

BEST MODE FOR CARRYING OUT THE INVENTION

[0085] Hereinafter, preferred embodiments of the present invention willbe described in detail with reference to the accompanying drawings.

[0086]FIG. 1 shows a device of circulation type for manufacturingcarbonated spring as an example of a diagram schematically showing anentire configuration of a preferable device of the present invention.Reference numeral 1 denotes a carbon dioxide gas cylinder, referencenumeral 2 denotes a pressure gauge, reference numeral 3 denotes apressure control valve, reference numeral 4 denotes a flow meter,reference numeral 5 denotes a flow control valve, reference numeral 6denotes a carbon dioxide gas introduction intake, reference numeral 7denotes a carbon dioxide gas dissolver, reference numeral 8 denotes ahot water introduction intake, reference numeral 9 denotes a circulationtype suction pump, reference numeral 10 denotes a carbonated springdischarge port, reference numeral 11 denotes a bath and referencenumeral 12 denotes hot water.

[0087]FIG. 2 is a diagram schematically showing an entire configurationof another preferred device of the present invention. Reference numeral1 denotes a carbon dioxide gas cylinder, reference numeral 2 denotes apressure gauge, reference numeral 3 denotes a pressure control valve,reference numeral 4′ denotes an electromagnetic valve, reference numeral5 denotes a flow control valve, reference numeral 6 denotes a carbondioxide gas introduction intake, reference numeral 7 denotes a carbondioxide gas dissolver, reference numeral 8 denotes a hot waterintroduction intake, reference numeral 9 denotes a circulation typesuction pump, reference numeral 10 denotes a carbonated spring dischargeport, reference numeral 11 denotes a bath, and reference numeral 12denotes hot water.

[0088] Water in the bath 11 is circulated by the circulation typesuction pump 9 through the carbon gas dissolver 7 and carbon dioxide gasis supplied into the carbon dioxide gas dissolver. By dissolving carbondioxide gas into water (hot water) so as to raise the concentration ofcarbon dioxide gas in water gradually, carbonated spring of an alwayshigh predetermined concentration is produced.

[0089]FIG. 3 is a diagram schematically showing an entire configurationof still another preferred device of the present invention, indicating aone-pass type carbonated spring producing device. Reference numeral 1denotes a carbon dioxide gas cylinder, reference numeral 2 denotes apressure gauge, reference numeral 3 denotes a pressure control valve,reference numeral 4 denotes a flow meter, reference numeral 5 denotes aflow control valve, reference numeral 6 denotes a carbon dioxide gasintroduction intake, reference numeral 7 denotes a carbon dioxide gasdissolver, reference numeral 8 denotes a hot water introduction port andreference numeral 10 denotes a carbonated spring discharge port.

[0090] Carbon dioxide gas is reduced to a predetermined pressure fromthe carbon dioxide gas cylinder 1 by the pressure control valve 3 andthe flow rate is controlled by the flow control valve 5. After that, itis fed into the carbon dioxide gas dissolver 7 through which hot waterflows so that it is dissolved in the hot water.

[0091] Although these devices may be provided with no pressure controlvalve 3, it is preferable to provide with it for the safety and forcontrol of the flow control valve 5, which is provided later. Althoughthe pressure control valve 3 is not restricted to any particular type,an ordinary pressure reduction valve, whish is installed directly on acylinder, may be accepted.

[0092] Pressure control of carbon dioxide gas applied on the membrane isnot required and what is important is control on the flow rate of carbondioxide gas flowing on the membrane. If the flow rate of the carbondioxide gas is regulated to constant, pressure applied on the membraneis high in the initial period of gas passage and thereafter, it dropsgradually. The membrane is stained each time when it is used, so thatthe pressure rises gradually, but the pressure of carbon dioxide gasapplied to the membrane does not affect manufacturing of carbonatedspring at a high precision.

[0093] Thus, flow control on the carbon dioxide gas flowing on themembrane is very important. As the flow control valve 3, various kindsof needle valves, for example, electronically used piezo or solenoidactuator can be picked up and although not particularly limited, aneedle valve is preferable because it is cheap. Further, it ispermissible to use an orifice having a throttle. The function of thisflow control valve 5 is important for the present invention andparticularly, even if the pressure or temperature changes, a mass flowrate type which has the function for always keeping the flow rateconstant is preferable. A pressure is applied when carbon dioxide gas isfed into the carbon gas dissolver and the pressure differs between inthe initial period of gas passage and at the stabilizing time. Thus, atype having this function can perform more stabilized flow control.

[0094] Although the flow control valve 5 can always control the flowrate to constant if its knob is fixed, it is preferable to provide witha flow meter because the flow meter can be checked visually and judgedinstantly when any trouble occurs. As the flow meter, a float typevolume flow meter and current temperature difference detection type massflow meter can be mentioned and although not limited, the mass flowmeter is more unlikely to be affected by the pressure and temperature.

[0095] Regarding the flow rate of carbon dioxide gas, in case of thecirculation type, the flow rate ratio between the flow rate of thecirculation pump and carbon dioxide gas is set to 2 to 20, preferably, 3to 10. Within this range, the dissolving efficiency is raised. If it issmaller than that range, the dissolving efficiency drops remarkably andconversely if it is larger, the dissolving efficiency is excellent butthe flow rate of the circulation pump is increased or the flow rate ofcarbon dioxide gas is decreased. Thus, consumption power is consumedwastefully or the production time is prolonged, which is not preferable.In case of one-pass type, the flow rate of carbon dioxide gas per unitmembrane area is set to be in a constant range.

[0096] As the carbon gas dissolver, a membrane module can be used.

[0097] Although as the configuration of the membrane in the carbon gasdissolver, flat membrane, tubular membrane, hollow yarn membrane, spiralmembrane and the like can be mentioned, the hollow yarn membrane is mostpreferable in terms of compactness of the device and ease of handling.

[0098] Various kinds of membranes may be used as long as they have anexcellent gas permeability, and both porous hollow yarn membrane andnonporous hollow yarn membrane are acceptable. If the porous hollow yarnmembrane is used, the diameter of an opening hole in its surface ispreferred to be 0.01 to 10 μm. The most preferable hollow yarn membraneis a three-layer composite hollow yarn membrane in which a thinnonporous gas permeable layer is sandwiched by porous layers on bothsides and its specific example is, for example, a three-layer compositehollow yarn membrane (MHT-200TL, product name) made by Mitsubishi RayonCo., Ltd.

[0099] The nonporous gas permeable layer (membrane) is a membrane whichgas passes by a dissolving/diffusion mechanism to its membrane substrateand any membrane is acceptable if molecules substantially do not containholes which gas can pass in a gas form like Knudsen flow. If thenonporous substance is used, the gas can be supplied and dissolvedwithout being emitted into carbonated spring as bubbles under any flowrate thereof and further dissolved effectively and controlled to anyconcentration because it can be dissolved easily. Although in case ofthe porous membrane, hot water sometimes backflows to the gas supplyside through pores, in case of the nonporous membrane, no hot waterbackflows to the gas supply side through the pores. In the three-layercomposite hollow yarn membrane, its nonporous layer is formed verythinly to have an excellent gas permeability and protected by poroussubstance so that it is hard to damage.

[0100] The gas permeation membrane is preferred to be of nonporousmembrane including no Knudsen flow, thereby there being no fear that themembrane turns hydrophilic during a long term usage, causing a waterleakage.

[0101] As described above, the membrane thickness of the nonporousmembrane is preferred to be in a range of 0.1 μm to 500 μm. If themembrane thickness is smaller than 0.1 μm, the membrane production andhandling are difficult. If the membrane thickness is larger than 500 μm,the vapor permeating amount drops while the carbon gas permeating amountdrops also, so that a very large membrane area is required to obtain anecessary performance.

[0102] Preferably, the membrane thickness of the hollow yarn membrane is10 to 150 μm. If it is less than 10 μm, membrane strength becomesinsufficient and if it exceeds 150 μm, the passing velocity of carbondioxide gas drops so that its diffusion efficiency is likely to drop. Incase of the three-layer composite hollow yarn membrane, the thickness ofthe nonporous membrane is 0.3 to 20 μm. If it is less than 0.3 μm,membrane deterioration is likely to occur and if the membrane isdeteriorated, leakage is likely to occur. If the membrane thicknessexceeds 20 μm, the passing velocity of carbon dioxide gas drops, whichis not preferable.

[0103] Examples of a preferable hollow yarn membrane material includesilicone base, polyolefin base, polyester base, polyamide base,polyimide base, polysulfone base, cellulose base, polyurethane base andthe like. Examples of the preferable materials of the nonporous membranein the three-layered composite hollow yarn membrane includepolyurethane, polyethylene, polypropylene, poly-4-methylpentene-1,polydimethylsiloxane, polyethyl cellulose, polyphenylene oxide and thelike. Particularly, polyurethane has an excellent membrane producingproperty with a small amount of eluted substance.

[0104] If the hollow yarn membrane is used for the carbon dioxide gasdissolver, there are a method in which carbon dioxide gas is suppliedinside pores in the hollow yarn membrane and hot water is supplied tothe side of the outer surface so as to dissolve carbon dioxide gas and amethod in which carbon dioxide gas is supplied to the side of the outersurface of the hollow yarn membrane and hot water is supplied insidepores so as to dissolve carbon dioxide gas. If carbon dioxide gas issupplied to the outer surface of the hollow yarn membrane while hotwater is supplied inside the pores so as to dissolve carbon dioxide gas,carbon dioxide gas can be dissolved in hot water at a high concentrationregardless of the configuration of the membrane module.

[0105] The inside diameter of the hollow yarn membrane is preferred tobe 50 to 1000 μm. If it is less than 50 μm, resistance of a flow path tocarbon dioxide gas or hot water flowing through the hollow yarn membraneis increased, so that supply of carbon dioxide gas or hot water isdisabled. Further, if it exceeds 1000 μm, the size of the dissolver isincreased, thereby not making it possible to achieve compactnessthereof.

[0106] In the carbon dioxide gas dissolver for use in the presentinvention, the gas diffusing portion composed of porous substance may beprovided with gas diffusing means installed on the bottom portion of thecarbon dioxide gas dissolver. Although the material and configuration ofthe porous substance disposed in the gas diffusing portion are notrestricted to any particular ones, porosity, namely, volume ratio to theentire porous substance of pores existing in the porous substance itselfis preferred to be in a range of 5 to 70 vol %. To raise the dissolvingefficiency of carbon dioxide gas, it is better as the porosity is lowerand it is preferred to be 5 to 40 vol %. If the porosity exceeds 70 vol%, it is difficult to control the flow rate of carbon dioxide gas sothat bubbles of carbon dioxide gas diffused from the porous substancebecome huge thereby likely decreasing the diffusing efficiency. If theporosity is less than 5 vol %, the supply amount of carbon dioxide gasdecreases and thus, it tends to take a long time to dissolve carbondioxide gas.

[0107]FIG. 4 is a sectional view showing an example of the hollow yarnmembrane module of the present invention. A hollow yarn membrane 21 isfixed to a fixing member 23 within a housing 20 with opening state atboth ends thereof kept and the side in which water flows and the side inwhich carbon dioxide gas is supplied are sealed by the fixing member 23such that no liquid is permitted to enter.

[0108] The housing 20 is provided with an intake 24 and an outlet 25communicating with a hollow portion in the hollow yarn membrane 21.Further, it is provided with an intake 26 and an outlet 27 communicatingwith the outer surface of the hollow yarn membrane 21.

[0109] As the gas permeation membrane used in the present invention, amembrane whose carbon dioxide gas permeating amount at 25° C. is 1×10⁻³to 1 m³/m²·hr·0.1 MPa is used. If the carbon dioxide gas permeatingamount is lower than 1×10⁻³ m³/m²·hr·0.1 MPa, carbon dioxide gas cannotbe dissolved in water efficiently and if it is higher than 1m³/m²·hr·0.1 MPa, a large amount of carbon dioxide gas permeates under alow pressure. Thus, even a small deflection in pressure is notpreferable because the permeating amount changes largely.

[0110] Further, the gas permeation membrane for use is a membrane whosevapor permeating amount at 25° C. is 1×10³g/m²·hr·0.1 MPa or less. Ifthe vapor permeating amount is higher than 1×10³g/m²·hr·0.1 MPa, anecessity of discharging drain out of the membrane module frequentlyoccurs, which is not preferable.

[0111] Furthermore, if the carbon dioxide gas permeating amount is1×10⁻² to 1×10⁻¹ m³/m²·hr·0.1 MPa and the vapor permeating amount is1×10² g/m²·hr·0.1 MPa or less, it is more preferable.

[0112] The vapor permeating amount and carbon dioxide gas permeatingamount mentioned here refer to weight of vapor and volume of the carbongas permeation membrane per unit area and unit time when differentialpressure of 0.1 MPa is applied between membranes at the ambienttemperature of 25° C.

[0113] If the carbon dioxide gas permeating amount is high in case ofthe membrane used for dissolving carbon dioxide gas conventionally, thevapor permeating amount is also high. Thus, if drain is discharged outof the membrane module frequently, the dissolving efficiency of carbondioxide gas cannot be maintained, and particularly in case of hot water,this problem is remarkable.

[0114] The configuration of the membrane is not restricted to anyparticular one but it may be formed into a desired configuration, forexample, hollow yarn membrane configuration, flat membrane configurationand other configurations as required. However, the hollow yarn membraneconfiguration is preferable because the membrane area per volume of themodule can be increased when it is processed to the module.

[0115] Although the membrane can be formed of only the nonporousmembrane for the reason for the stiffness and thickness of the materialof the gas permeation membrane, if the membrane thickness is minute orit is, for example, of flat membrane in order to protect the membranesurface, it is permissible to use a reinforcement porous substance as aspacer. If it is formed of the hollow yarn membrane, it is possible toform to a multi-layer membrane by providing a supporting layer forsupporting the hollow yarn membrane on the inner surface and/or theouter surface. These methods may be selected appropriately.

[0116]FIG. 5 shows an example of the desirable configuration of themembrane used for the present invention, which is a composite hollowyarn membrane 21 comprised of three layers while having porous layers 21b on both sides of a nonporous layer 21 a. Because in such a compositehollow yarn membrane 21, both faces of the gas permeating nonporousmembrane 21 a are protected by the porous membrane 21 b, the nonporouslayer is not directly touched at the time of processing or handling foractual usage, so as to protect the membrane from damage or contaminationand further, the obtained hollow yarn membrane has an excellentmechanical strength also.

[0117] Examples of a gas permeating nonporous membrane material includea nonporous membrane composed of segmented polyurethane or polymer blendof styrene base thermoplastic elastomer and polyolefin. Morespecifically, (S)-(EB)-(S) tri-block copolymer composed of copolymer(EB) produced by styrene base thermoplastic elastomer's hydrogenatingstyrene copolymer (S) and butadiene copolymer, nonporous membrane, whichis (S)-(BU)-(S) tri-block copolymer composed of styrene copolymer (S)and butadiene copolymer (BU), polymer produced by hydrogenating randomcopolymer composed of styrene monomer and butadiene monomer, randomcopolymer composed of styrene monomer and butadiene monomer and the likecan be mentioned.

[0118] As for the composition ratio of styrene base thermoplasticelastomer and polyolefin, it is preferable that styrene basethermoplastic elastomer is 20 to 95 mass portion and polyolefin is 80 to5 mass portion with respect to 100 mass portion which is total of boththe compositions and more preferably, the styrene base thermoplasticelastomer is 40 to 90 mass portion while the polyolefin is 60 to 10 massportion.

[0119] When the composite hollow yarn membrane is used, as a polymermaterial which constitutes a porous layer, it is permissible to usepolyethylene, polypropylene, polyolefin base polymer such aspoly(3-methylebutene-1) and poly(4-methylpentene-1), polyvinylidenefluoride, fluoro base polymer such as polytetrafluorethylene,polystyrene, and polymer such as polyether ether keton and polyetherketon.

[0120] As regards the membrane forming method, an appropriate knownmembrane forming method may be selected depending on the formability,moldability and the like of the material. If taking an example offorming a hollow yarn membrane configuration, a material of a carbondioxide gas adding membrane is extruded in a molten state from a hollowpipe sleeve and after cooling, wound up according to a conventionallywell known method.

[0121] To dissolve carbon dioxide gas into water, water is fed to onesurface of the gas permeation membrane and carbon dioxide gas is appliedwith a pressure to the other surface thereof. If the hollow yarnmembrane is used, it is permissible to adopt a method in which water isfed into the hollow portion in the hollow yarn membrane while carbondioxide gas is applied to the outside of the hollow yarn membrane(hereinafter called internal circulation method) or it is permissible toadopt a method in which liquid is fed outside the hollow yarn membranewhile carbon dioxide gas is applied to the hollow portion (hereinafter,called external circulation method). Any one of these methods may beused.

[0122] If the hollow yarn membrane module 20 having the structure shownin FIG. 4 is used, in case of the internal circulation method, water issupplied to the hollow portion in the hollow yarn membrane 21 from theintake 24 and further, carbon dioxide gas is supplied under anappropriate pressure to the outside of the hollow yarn membrane 21 fromthe intake 26. Consequently, water in which carbon dioxide gas isdissolved can be obtained from the outlet 25. The outlet 27 is usuallyclosed at this time and opened as a drain discharge port if necessary todischarge water which permeates as vapor.

[0123] In case of the external circulation method, carbon dioxide gas issupplied into the hollow portion in the hollow yarn membrane 21 from theintake 24 and water is supplied to the outside of the hollow yarnmembrane 21 from the intake 26 and then, water in which carbon dioxidegas is dissolved is obtained from the outlet 27. At this time, usually,the outlet 25 is closed and then opened as a drain discharge portappropriately to discharge water which permeates as vapor.

[0124] The drain discharge port is preferred to be disposed at aposition which allows drain collected in a space on the side of thecarbon dioxide gas in the hollow yarn membrane module to be dischargewithout any remaining and provided at a position located on the bottomwhen a module is provided.

[0125] In some case, the drain discharge port is provided with anopening/closing valve which is closed when carbon dioxide gas is addedand opened/closed manually as required. In other case, it is providedwith an electromagnetic valve, which is opened or closed every specifiedtime or may be automatically opened when a predetermined amount of drainis collected by a water level sensor or the like which is installed in aspace on the gas side.

[0126] As for the discharge of drain, after the supply of carbon dioxidegas is stopped, water can be discharged using a remaining pressure ofcarbon dioxide gas remaining in the membrane module. If the drain isdischarged too frequently at this time, the amount of carbon dioxidewhich is discharged out of the module together with the drain andconsumed without being dissolved in water is increased. Thus, it iseconomically important to use a membrane having a low vapor permeabilityto avoid the drain discharge if possible.

[0127] Particularly, in case of the external circulation method, drainis collected inside the hollow yarn membrane and the volume in whichdrain is deposited is smaller than the internal circulation method.Thus, the permeating vapor amount is small and therefore, using amembrane generating not so much drain is very effective.

[0128] Preferably, the membrane density inside the carbon dioxide gasadding membrane module is set in a range of 2000 to 7000 m²/m³ in orderto allow carbon dioxide gas or water contact the membrane surfaceeffectively and keep water feeding pressure loss in an appropriaterange.

[0129] Further, the internal circulation method has such an effect thatdrain is moved to the bottom of the module without any remaining by itsweight and discharged in a short time in addition to an effect thatcarbon dioxide gas can be dissolved efficiently by keeping the membranedensity in this range.

[0130] More preferably, the membrane density is in a range of 4000 to6000 m²/m³.

[0131] The membrane density of the membrane module refers to a valueobtained by dividing the membrane area of the membrane module by thevolume of the membrane module. In the meantime, the membrane area of themembrane module refers to the total area of the membrane surface, whichis a larger one of the side in contact with liquid or the side in whichgas is supplied. In case of the composite hollow yarn membrane havingthree layers in which the porous layers are disposed on both sides ofthe aforementioned nonporous layer, it refers to a sum of the outsidesurface area of the porous layer.

[0132] The volume of the membrane module refers to the volume of a spacein which the hollow yarn membrane 21 is disposed excluding connectionportions for suction or liquid feeding in case of the membrane moduleintegrated with the housing 20. In case of a type which is accommodatedin a cylindrical housing 20l having plural slits like an ordinary10-inch cartridge, it refers to the volume of a space in which thehollow yarn membrane 21 is disposed within the cylindrical housing.

[0133] It is described that there exists a blood flow rate increaseeffect when carbon dioxide gas concentration exceeds about 300 mg/l asdescribed in “The effects of external CO₂ application on human skinmicrocirculation investigated by laser Doppler flowmetry. Int JMicrocirc: Clin Exp 4:343-350 (1985)” and the carbon dioxide gasconcentration is preferred to be 300 mg/l or more.

[0134] On the other hand, the saturated solubility of carbon dioxide gasat 40° C. is about 1300 mg/l, and even if more carbon dioxide gas thanthis concentration is added, the dissolving efficiency drops so thatundissolved gas is spouted from the outlet together with water, which isnot preferable.

[0135] As for the method for adjusting a carbon dioxide gasconcentration, it can be adjusted easily by adjusting the supplypressure of carbon dioxide gas with such a pressure adjusting unit as aregulator.

[0136] If water temperature is raised after gas is added, dissolved gasreturns to bubbles so that the gas concentration in water drops, whichis not preferable. Thus, the temperature of water flowing through thewater path is preferred to be adjusted in a range of 30° C. to 50° C.

[0137] If the water temperature is 30° C. or higher, generally,discomfort is not felt when the skin makes contact with the water infoot bathing or taking shower. If water is not used just after carbondioxide gas is added, it is permissible to add carbon dioxide gas attemperatures about 50° C. and adjust the water temperature to a suitableone by allowing it to cool. A preferable temperature range is from 35°C. which is a temperature around the human temperature to 40° C.

[0138] Because the vapor permeating amount increases as the temperatureincreases, the carbon dioxide gas adding module of the present inventioncan be used preferably when carbon dioxide gas is dissolved into hotwater.

[0139] The diameter of an opening in the surface of the porous substanceis preferred to be 0.01 to 10 μm in order to control the flow rate ofdiffused carbon dioxide gas and form minute bubbles. If the holediameter exceeds 10 μm, bubbles rising in water become too large,thereby the dissolving efficiency of carbon dioxide gas being likely todrop. Further, if it is less than 0.01 μm, the diffused amount in waterdecreases so that carbonated spring having a high concentration islikely to be impossible to obtain.

[0140] The porous substance disposed in the diffusing portion of thediffusing means is capable of generating more bubbles as the surfacearea thereof is larger, so that contact between carbon dioxide gas andhot water is progressed efficiently and further, dissolving beforegeneration of the bubbles is progressed, thereby intensifying thedissolving efficiency. Therefore, although the configuration of theporous substance is not restricted to any particular one, it is morepreferable as the surface area is larger. Although as means forenlarging the surface area, there are various methods, for example, amethod of forming the porous substance cylindrically and a method offorming a flat shape and providing its surface with unevenness, it ispreferable to use the porous hollow yarn membrane and particularly,using a bundle of multiple porous hollow yarn membranes is effective.

[0141] As the material of the porous substance, various kinds ofmaterials, such as metal, ceramic and plastic can be mentioned.Hydrophilic material is not preferable because hot water invades intothe diffusing means through pores in the surface when the supply ofcarbon dioxide gas is stopped.

[0142] Although the temperature of hot water for use is not restricted,preferably, it is from 30 to 45° C. and more preferably, it is 35 to 40°C. because the highest heat insulation effect is secured.

[0143] Some types of instruments for measuring the concentration ofcarbon dioxide gas dissolved in water have been well known. Acirculation type carbon dioxide gas concentration meter comprises acarbon dioxide gas electrode and a carbon dioxide gas concentrationindicator. Electrode membrane and internal liquid need to be replacedevery one to three months, so that its maintenance takes time and laborand the cost is high. Further, because it is disadvantageous formeasurement of a high concentration, it lacks practical performance as ameasuring instrument for use in the device for manufacturing carbonatedspring.

[0144] A thermal conductivity detection type carbon dioxide gasconcentration meter used in a carbonic beverage manufacturing device isvery expensive and not suitable for measurement of the concentration ofcarbonated spring. As a low cost method, there is a method ofcalculating according to alkaline degree and pH of raw water used forcarbonated spring. Carbon dioxide gas concentration in carbonated springand pH of carbonated spring have a specified relation and the relationbetween the carbon dioxide gas concentration and pH of carbonated springchanges depending on the alkaline degree of raw water. Thus, to obtainthe carbonic acid concentration from pH, the alkaline degree of the rawwater needs to be measured. However, if this is obtained, the carbondioxide gas concentration can be measured easily from pH. Generally, therelation among alkaline degree, pH and carbon dioxide gas concentrationis established by a following Tillman's expression.

Carbon dioxide gas concentration (mg/l)=10^(log[alkaline degree (CaCO)^(₃) ^(mg/l)]+6.31−pH)

[0145] Generally, the alkaline degree of raw water is not changed somuch with a time passage if that is water obtained from a certain watersource such as tap water. Thus, if a carbonated spring manufacturingdevice is installed and the alkaline degree of raw water is measuredbefore this is started, the value can be used after that. Of course, thealkaline degree of raw water may be obtained each time when thecarbonated spring manufacturing device is used. In the meantime, thealkaline degree mentioned here is a way for indicating the amount ofcontent of component which consumes acid such as OH, CO₃ ²⁻, HCO₃ andthe like contained in raw water and it is preferable to adopt pH 4.8alkaline degree (M alkaline degree). For this method, pH needs to beanalyzed at a high precision and its error needs to be suppressed within±0.5 and more preferably, within ±0.01. Therefore, it is preferable tocalibrate periodically, preferably each day of usage.

[0146] As another style of the carbon dioxide gas dissolver, a staticmixer can be mentioned. The static mixer is for separating fluidmechanically to diffuse carbon dioxide gas and not clogged in terms ofits structure even if a foreign matter is mixed in fluid so that it canbe used for long hours. The detail of the static mixer is described inChapter 1 of, for example, Basic and Application of Static Mixer,supervised by Shingo Hagiwara, issued by Nikkan Kogyo Shinbunsha (firstedition is published Sep. 30, 1981).

[0147] Although the solubility of carbon dioxide gas differs dependingon the performance of the dissolver, in case of circulation type, it isdetermined depending on the supply velocity of water supplied to thecarbon dioxide gas dissolver, namely, the ratio between the flow rate ofthe circulation pump and the supply velocity of carbon dioxide gassupplied to the dissolver. The lower the ratio between the carbondioxide gas supply velocity and water supply velocity, the higher thesolubility is. If the water supply velocity is constant, the carbondioxide gas supply velocity needs to be reduced to reduce the ratiobetween the carbon dioxide gas supply velocity and the water supplyvelocity. In this case, there is a disadvantage that manufacturing timeis prolonged. However, the relation between the ratio between the carbondioxide gas supply velocity and water supply velocity and the solubilitydiffers depending on the concentration of carbon dioxide gas in watercirculated to the dissolver. As the concentration is lower, thesolubility keeps excellent even if the ratio between the carbon dioxidegas supply velocity and water supply velocity is low and as theconcentration is increased, the solubility drops unless the ratiobetween the carbon dioxide gas supply velocity and water supply velocityis increased. According to a prior art, carbon dioxide gas is suppliedat the same supply velocity from a manufacturing startup to the endthereof without considering such a matter and by changing the carbondioxide gas supply velocity halfway, carbonated spring can bemanufactured at an excellent solubility.

[0148] For example, the carbon dioxide gas supply velocity at a startupof manufacturing is increased and when 10 to 50% the manufacturing timeis passed, the supply velocity of the carbon dioxide gas is reduce toabout ½ to {fraction (1/10)}. By executing this operation, it ispossible to improved the solubility and reduce the consumption of thecarbon dioxide gas without prolonging the manufacturing time. This isjust an example and the carbon dioxide gas supply velocity can bechanged through multi-stages.

[0149] To change the carbon dioxide gas supply velocity halfway in thisway, plural carbon dioxide gas supply velocity means are provided inparallel as shown in FIG. 2 and in front half of the manufacturing time,an electromagnetic valve 4′ for which the carbon dioxide gas supplyvelocity is set fast by the flow control valve 5 is opened in order toaccelerate the carbon dioxide gas supply velocity while the other valveis closed. In rear half of the manufacturing time, an electromagneticvalve 4′ for which the carbon dioxide gas supply velocity is set slow isopened in order to retard the carbon dioxide gas supply velocity whilethe other valve is closed. Although two flow control valves 5 are usedhere, it is permissible to control with three or more flow controlvalves.

[0150] In this indicated example, the circulation pump 9 is necessaryfor manufacturing carbonated spring in the circulation system. As thepump, a volume type proportioning pump having a self suction performanceis preferable. Using this enables stabilized circulation and alwaysconstant circulating water quantity to be achieved. Although if thecarbonated spring is dense, bubbles are more likely to occur so that abubble rich state is generated, even in this case, stabilized waterfeeding is achieved if a pump having self suction performance which canbe started without priming at the initial operation time is used.

[0151] In case where artificial carbonated spring is manufacturedcontinuously, the artificial carbonated spring having a predeterminedcarbon dioxide gas concentration can be manufactured by combining themeans for measuring the carbon dioxide gas concentration and the methodof manufacturing the artificial carbonated spring. As the method formeasuring the concentration of carbon dioxide gas in water, measurementbased on the ion electrode system is a general method. However,measurement in line and on time is impossible because it takes a longtime until the ion electrode is balanced in a solution having a highconcentration required by the artificial carbonated spring and anaccurate measurement is impossible as gas bubbles adhere to the ionelectrode.

[0152] Hereinafter, a carbonated spring continuous manufacturing deviceequipped with the carbon dioxide gas concentration measuring device of atypical embodiment of the present invention will be described withreference to the accompanying drawings. According to this embodiment,the example of the artificial carbonated spring will be described. Thegas concentration measuring method and gas dissolved solutionmanufacturing device of the present invention are not restricted to theartificial carbonated spring but may be applied to gas concentrationmeasurement of any solution obtained by dissolving gas regardless of thekind of the gas.

[0153]FIG. 6 is a diagram showing a configuration of the artificialcarbonated spring manufacturing device of the present invention.

[0154] As shown in the same figure, a take-in pipe A and a return pipe Bfor circulating hot water 12 (after carbon dioxide gas is dissolved,turns to artificial carbonated spring) loaded in the bath 11 as astorage bath for the artificial carbonated spring communicate with theinside of the bath. Part of the return pipe B is constituted as atake-out pipe 15 from the carbon dioxide gas dissolver 7. The hot water12 in the bath 11 is pumped up through the take-in pipe A by the suctionpump 9 and a predetermined amount of the hot water 12 is introduced intothe carbon dioxide gas dissolver 7 as a gas dissolver through solutionflow rate adjusting means 14.

[0155] Carbon dioxide gas supplied from the carbon dioxide gas cylinder1 is adjusted in pressure by the pressure adjusting means 3 and thecarbon dioxide gas discharged from the pressure adjusting means 3 isadjusted in terms of the flow rate by the gas flow rate adjusting means5 and then introduced into the carbon dioxide gas dissolver 7. Detectionvalues detected by the pressure gauges 2 provided before and after thepressure adjusting means 3 are inputted to the control device 16 andthen, the pressure adjusting means 3 is controlled by a control signalfrom the same control device 16 so as to adjust the pressure of thecarbon dioxide gas.

[0156] Artificial carbonated spring discharged from the carbon dioxidegas dissolver 7 through the take-out pipe 15 and containing bubbles issubjected to measurement about the quantity of bubbles of carbon dioxidegas in the take-out pipe 15 by a measuring device 13 and returned intothe bath 11 through the artificial carbonated spring discharge port 10.

[0157] The measuring device 13 is provided with an ultrasonic wavetransmitter and an ultrasonic wave receiver disposed across the take-outpipe 15 and ultrasonic wave dispatched from the ultrasonic wavetransmitter is received by the ultrasonic wave receiver so as to measurethe strength of the received ultrasonic wave. A measurement valueobtained by the measuring device 13 is inputted to the control device16.

[0158] The control device 16 computes the carbon dioxide gasconcentration in the artificial carbonated spring discharged into thetake-out pipe 15 according to a relational expression between thequantity of bubbles in carbon dioxide gas preliminarily measured(damping rate of ultrasonic wave received by ultrasonic wavereceiver=(strength of ultrasonic wave signal received by ultrasonic wavereceiver)/(strength of ultrasonic wave signal dispatched from ultrasonicwave transmitter): measured in terms of %) and a measured value of thecarbon dioxide gas concentration in the artificial carbonated springdischarged from the carbon dioxide gas dissolver 7, corresponding to theflow rate of the hot water 12 introduced into the carbon dioxide gasdissolver 7 and the introduction amount of carbon dioxide gas.

[0159] Corresponding to the carbon dioxide gas concentration of theartificial carbonated spring by the control device 16, the solution flowrate adjusting means 14, the suction pump 9, the gas flow rate adjustingmeans 5 and the pressure adjusting means 3 are controlled so as toadjust the carbon dioxide gas concentration of the artificial carbonatedspring discharged from the carbon dioxide gas dissolver 7. When thecarbon dioxide gas concentration of the same artificial carbonatedspring reaches a desired carbon dioxide gas concentration, the suctionpump 9 and the pressure adjusting means 3 are controlled to endintroduction of the hot water 12 and carbon dioxide gas into the carbondioxide gas dissolver 7.

[0160] Instead of using the carbon dioxide gas cylinder 1, it ispermissible to use carbon dioxide gas obtained by condensing carbondioxide gas in combustion gas from combustion in a combustion device. Inthis case, the concentration of the condensed carbon dioxide gas needsto be kept constant.

[0161] As the pressure control means 3, a pressure control valve or thelike may be used. As the gas flow rate adjusting means 5 and thesolution flow rate adjusting means 14, a flow rate adjusting valve orthe like may be used. As the gas dissolver 7, a well known gas dissolvermay be used and using the static mixer or hollow yarn membrane typedissolver enables the solubility of the dissolver to be intensified.Further, it is permissible to provide a pressure adjusting means in thedownstream of the suction pump 9 of the take-in pipe A and pressuregauges before and after the same pressure adjusting means to control thepressure adjusting means by the control device 16 according to detectionvalues from the same pressure gauges.

[0162] It is permissible to provide the bath 11 with a faucet (notshown) to pour hot water additionally or provide with a combustiondevice for hot water to warm up the hot water. Although FIG. 6 shows theconfiguration for circulating the hot water 12 to the carbon dioxide gasdissolver 7, it is possible to manufacture artificial carbonated springby supplying hot water from a hot water supply source (not shown) to thecarbon dioxide gas dissolver 7. It is permissible to arrange the carbondioxide gas dissolvers in multi-stages in series to manufacture theartificial carbonated spring. In these cases, by disposing a measuringdevice on the take-out pipe from the carbon dioxide gas dissolver, thecarbon dioxide gas concentration of the artificial carbonated springdischarged from the respective carbon dioxide gas dissolvers can bemeasured.

[0163]FIG. 7 is a diagram showing the relational expression between thedamping rate of the ultrasonic wave signal received by the ultrasonicwave receiver contained in the measuring device 13 and the measurementvalue of the carbon dioxide gas concentration of the artificialcarbonated spring flowing through the take-in pipe A. The samerelational expression is obtained under a condition that the flow rateof carbon dioxide gas introduced into the carbon dioxide gas dissolver 7and the flow rate of hot water are constant. Because the dissolvingcondition changes depending on the pressure of carbon dioxide gasintroduced into the carbon dioxide gas dissolver 7, the pressure of hotwater, dissolving capacity of the carbon dioxide gas dissolver,temperature and pressure at the time of dissolving within the carbondioxide gas dissolver 7 and the like, it is desirable to set up thecondition for manufacturing the artificial carbonated springpreliminarily with the gas dissolver 7 and obtain the aforementionedrelational expression under the set condition.

[0164] In the meantime, the present invention may be applied tomanufacturing other than that of the artificial carbonated spring and inthis case, it is necessary to obtain a relational expression between thequantity of bubbles and gas concentration by measuring under themanufacturing condition corresponding to the condition for manufacturinga solution.

[0165] As evident from FIG. 7, with a rise of the carbon dioxide gasconcentration of the artificial carbonated spring introduced to thecarbon dioxide gas dissolver (the carbon dioxide gas concentration ofthe artificial carbonated spring taken out of the carbon dioxide gasdissolver rises correspondingly because the dissolving condition in thedissolver is constant), the mixing amount (that is, quantity of bubbles)of undissolved gas in the artificial carbonated spring increases, sothat the ultrasonic wave signal dispatched from the ultrasonic wavetransmitter is damped and received by the ultrasonic wave receiver. Afollowing will be described again and to mix the non-dissolved gas intothe artificial carbonated spring, the carbon dioxide gas needs to beintroduced by a flow rate not less than the maximum dissolving amount bythe carbon dioxide gas dissolver 7.

[0166] The reception signal by the ultrasonic wave transmitterincorporated in the measuring device 13 is subjected to the signalprocessing shown in FIG. 8. That is, after a signal received by theultrasonic wave receiver is amplified and smoothed, signal values aftera predetermined time interval are integrated and then, a value obtainedby the integration (handled as a voltage value) is compared with apreliminarily set voltage value. By this comparison, it can be detectedthat the damping rate of the ultrasonic wave signal is a set value orless, or the carbon dioxide gas concentration of the artificialcarbonated spring is a desired carbon dioxide gas concentration or more.

[0167] Although the carbon dioxide gas concentration in hot water riseswith a passage of the circulation time, artificial carbonated springhaving a desired carbon dioxide gas concentration can be always obtainedby controlling the ON/OFF of the suction pump 9 according to thedetection signal from the measuring device 13. Further, by pouring hotwater directly from a supply unit such as a faucet into the bath tochange the ratio between the quantity of hot water of the artificialcarbonated spring and the supply amount of the carbon dioxide gasaccording to the detection signal of the measuring device 13, theartificial carbonated spring having a desired carbon dioxide gasconcentration can be produced.

EXAMPLES

[0168] Hereinafter, the present invention having the diversifiedembodiments will be described more specifically with reference to theexamples.

[0169] First, an example of the carbon dioxide gas adding membranemodule applied to the device of the present invention will be describedspecifically.

[0170] (Experiment No. 1)

[0171] With polymer blend composed of styrene base thermoplasticelastomer and polypropylene (made by DAI-NIPPON PLASTICS Co., Ltd.,product name MK resin MK-2F (Tg=−35° C., composition ratio: (S)-(EB)-(S)tri-block copolymer 50 mass portion, composed of polymer (EB) obtainedby hydrogenating styrene polymer (S) and butadiene polymer, as styrenebase thermoplastic elastomer and atactic polypropylene 50 mass portionas polyolefin) as a material for a nonporous layer and polyethylene(made by TOSOH CORPORATION, product name: NIPORON HARD 5110) as amaterial for a porous layer, a three-layered composite hollow yarnmembrane shown in FIG. 5 having the outside diameter of 300 μm, theinside diameter of 180 μm and the nonporous layer thickness of 2 μm wasmanufactured.

[0172] The carbon dioxide gas permeating amount of this composite hollowyarn membrane was 3.3×10⁻² m³/m²·hr·0.1 MPa and the vapor permeatingamount was 22 g/m²·hr·0.1 MPa.

[0173] The carbon dioxide gas adding hollow yarn membrane module shownin FIG. 4 was produced using the obtained composite hollow yarn membranesuch that the hollow yarn membrane area was 0.71 m², the volume was1.6×10⁻⁴ m³ and the membrane density was 4438 m²/m³. An intermittentoperation of supplying water of 40° C. by a flow rate of 5 l/min to thehollow portion in the hollow yarn membrane for three minutes whilesupplying carbon dioxide gas with a pressure of 0.36 MPa at 1.25 l/minand then interrupting the supplies of carbon dioxide gas and water for57 minutes, which is a cycle of an hour was carried out continuously for1000 hours.

[0174] When 20% the effective length of the hollow yarn membrane wassubmerged in water, the drain discharge port was opened for first oneminute of 57-minute stop time to discharge drain using remaining carbondioxide gas pressure. All drain in the module was discharged in the opentime of a minute.

[0175] Table 1 shows the generation amount per unit time of drainpermeated to the carbon dioxide gas supply side, the frequency of draindischarge and the use amount of carbon dioxide gas.

[0176] (Experiment No. 2)

[0177] With thermoplastic segmented polyurethane (made by ThermedicsInc. product name; Tecoflex EG80A) as the material of the nonporouslayer and polyethylene (made by Tosoh Corporation, product name: NiporonHard 5110) as the material of the porous layer, the three-layeredcomposite hollow yarn membrane shown in FIG. 5 having the outsidediameter of 300 μm, the inside diameter of 180 μm and the nonporouslayer thickness of 15 μm was produced.

[0178] The carbon dioxide gas permeating amount of the obtainedcomposite hollow yarn membrane was 1.6×10⁻² m³/m²·hr·0.1 MPa and thevapor permeating amount was 4.23×10² g/m²·hr·0.1 MPa.

[0179] The same carbon dioxide gas adding hollow yarn membrane asExperiment No. 1 was produced using this membrane and the same operationas Experiment No. 1 was carried out.

[0180] Table 1 shows the generation amount per unit time of drainpermeating the carbon dioxide gas supply side, the frequency of draindischarge and the use amount of carbon dioxide gas.

[0181] (Experiment No. 3)

[0182] A composite hollow yarn membrane having the same three-layeredstructure as Experiment No. 2 except that the thickness of the nonporouslayer was 1 μm was produced.

[0183] The carbon dioxide gas permeating amount of the obtainedcomposite hollow yarn membrane was 2.6×10⁻¹ m³/m²·hr·0.1 MPa and thevapor permeating amount was 6.8×10³ g/m²·hr·0.1 MPa.

[0184] The same carbon dioxide gas adding hollow yarn membrane module asExperiment No. 1 was produced using this membrane and the same operationas Experiment No. 1 was carried out.

[0185] Table 1 shows the generation amount per unit time of drainpermeating to the carbon dioxide gas supply side, the frequency of draindischarge and the use amount of carbon dioxide gas. TABLE 1 Draindischarge Carbon dioxide Drain amount frequency gas use amount ml/minTime/1000 hr kg/1000 hr Experiment No. 1 0.003 12 7.5 Experiment No. 20.08 320 7.9 Experiment No. 2 0.77 3000 10.5

[0186] By using the carbon dioxide gas adding membrane module of thepresent invention as shown in Table 1, the consumption of carbon dioxidegas could be reduced.

[0187] The carbon dioxide gas adding membrane module of the presentinvention enables carbon dioxide gas to be added into water even whenhot water is fed because a membrane whose carbon dioxide gas permeatingamount at 25° C. was 1×10⁻³ to 1 m³/m²·hr·0.1 MPa and whose vaporpermeating amount at 25° C. was 1×10³ g/m²·hr·0.1 MPa or less was used.Because the amount of vapor permeating the membrane is small and drainis unlikely to be deposited on the gas side, the frequency of draindischarges and the amount of carbon dioxide gas discharge into theatmosphere at the time of drain discharge can be reduced. Accordingly,the carbon gas additive water can be obtained at a high efficiency for along time, so that the module can be applied widely to applications foradding carbon dioxide gas to low temperature water, normal temperaturewater and further high temperature water.

[0188] Further, because the membrane density of the carbon dioxide gasadding module is in a range of 2000 to 7000 m²/m³, drain can bedischarged smoothly while maintaining the dissolving efficiency of thecarbon dioxide gas high.

[0189] If carbon dioxide gas is dissolved after water is heated to 30°C. to 50° C. preliminarily, carbon dioxide gas can be dissolvedefficiently.

[0190] Next, a typical embodiment of the carbonated spring manufacturingdevice of the present invention will be described. The carbon dioxidegas concentration of the carbonated spring was obtained according toTillman's expression by measuring alkaline degree and pH.

[0191] (Experiment No. 4)

[0192] Carbonated spring was produced with the circulation type deviceshown in FIG. 1. The carbon dioxide gas pressure was controlled to 0.4MPa with a pressure control valve. As a flow meter, an electronic massflow meter (CMS0020) made by Yamatake Hanewel Co., Ltd. was used and asa flow control valve, a mass flow control valve (MODEL 2203) made byKOFLOK K.K. was used to control the carbon dioxide gas flow rate to 1.0l/min (converted under 20° C.). As a dissolver, non-used hollow yarnmodule product made with a three-layered composite hollow yarn membrane(made by Mitsubishi Rayon Co., Ltd.) whose membrane area was 0.6 m² wasused. Hot water at 40° C. was poured into the bath by 10 l and the hotwater was returned to the bath by 5 l every minute by means of a suctionpump.

[0193] Table 2 shows the result obtained 10 minutes after circulation.The first time in Table 2 indicates the result collected first in theexperiment and the second time indicates the result collected after thefirst time. Both indicated the same carbon dioxide concentration.

[0194] (Experiment No. 5)

[0195] The flow control valve of Experiment No. 4 was released tocontrol the carbon dioxide gas supply amount with pressure. The pressurewas controlled to 0.15 MPa. Table 2 shows the result thereof. The carbondioxide gas concentration was low at the first time and high at thesecond time. TABLE 2 Carbon dioxide gas Frequency concentration (mg/l)Experiment No. 4 First time 1310 Second time 1310 Experiment No. 5 Firsttime 1040 Second time 1230

[0196] (Experiment No. 6)

[0197] This experiment was executed in the same manner as in ExperimentNo. 4 except that the flow rate of the circulation pump was 1 l everyminute, that is, the ratio between the flow rate of the circulation pumpand the flow rate of the carbon dioxide gas was set to 1. At the firsttime, the carbon dioxide gas concentration dropped to 700 mg/l, so thatthe dissolving efficiency was reduced remarkably.

[0198] (Experiment No. 7)

[0199] Carbonated spring was produced with the one-pass type deviceshown in FIG. 3. The carbon dioxide gas pressure was controlled to 0.4MPa with the pressure control valve. With the electronic mass flow meterCMS0020 made by Yamatake Hanewel Co., Ltd. as a flow meter and the floatcontroller MODEL 2203 made by KOFLOK K.K. as a flow control valve, thecarbon dioxide gas flow rate was controlled to 5.0 l/min (convertedunder 25° C.)

[0200] A hollow yarn module produced with the three-layered compositehollow yarn membrane (made by Mitsubishi Rayon Co., Ltd.) whose membranearea was 2.4 m² was used as a dissolver. Water at 400 was fed to thedissolver at 5 l/min. Table 3 shows the result thereof. Carbon dioxidegas concentration was stabilized about two minutes after water was fedfirst.

[0201] (Experiment No. 8)

[0202] The flow control valve of Experiment No. 7 was opened to controlthe carbon dioxide gas supply amount with a pressure. The pressure wascontrolled to 0.28 MPa. Table 3 shows the result thereof. The carbondioxide gas concentration in the initial period of water feeding wasunstable as compared with Example 4, so that the carbon dioxide gasconcentration was not stabilized even if 10 minutes passed after waterwas fed first. TABLE 3 Water feeding time 1 2 3 5 7 10 Experiment No. 71190 1210 1210 1210 1210 1210 Experiment No. 8 610 820 940 1100 11601200

[0203] Carbon Dioxide Gas Concentration (mg/l)

[0204] (Experiment No. 9)

[0205] The same operation as Experiment No. 4 was carried out with amodule used for 500 hours and its result was compared with the result ofExperiment No. 4 using the unused product. Table 4 shows the resultthereof. The same performance as the unused product was obtained.

[0206] (Experiment No. 10)

[0207] The same operation as Experiment No. 5 was carried out with amodule used for 500 hours and its result was compared with the result ofExperiment No. 5 using the unused product. Table 4 shows the resultthereof. The carbon dioxide gas concentration dropped as compared withthe unused product. TABLE 4 Use time Carbon dioxide gas (min)concentration (mg/l) Experiment No. 4 0 1310 Experiment No. 9 500 1290Experiment No. 5 0 1040 Experiment No. 10 500 980

[0208] Next, an example about the dissolving efficiency of carbondioxide gas will be described specifically. The carbon dioxideconcentration in carbonated spring was obtained according to Tillman'sexpression by measuring alkaline degree and pH. Table 5 shows asummarized result. Meanwhile, the dissolving efficiency in Table 5 wasobtained from “dissolving efficiency (%)=carbon dioxide gas dissolvingamount in carbonated spring/amount of used carbon dioxide gas×100”.

[0209] (Experiment No. 11)

[0210] Carbonated spring was produced with the circulation type deviceshown in FIG. 2. The carbon dioxide gas pressure was controlled to 0.4MPa with the pressure control valve. Two mass flow control valves (MODEL2203) made by KOFLOK K.K. were used as the flow control valves and thecarbon dioxide gas flow rate of one of them was adjusted to 2.0 l/min(converted under 20°) while the other was adjusted to 0.5 l/min(converted under 20°). As the dissolver, a hollow yarn module producedwith the three-layered composite hollow yarn membrane (made byMitsubishi Rayon Co., Ltd.) whose membrane area was 0.6 m² was used. Hotwater at 40° C. was poured into the bath up to 10 l and the hot waterwas returned to the bath by 5 l every minute by means of the circulationpump.

[0211] An electromagnetic valve was opened for carbon dioxide gas toflow to the flow control valve adjusted to 2.0 l/min at the startup ofmanufacturing while the other valve was closed. Up to the end 2 minutesto 10 minutes after, the electromagnetic valve was opened for carbondioxide gas to flow to the flow control valve adjusted to 0.5 l/minwhile the other valve was closed. Table 5 shows its result.

[0212] (Experiment No. 12)

[0213] This experiment was carried out in the same manner as inExperiment No. 11 except that the carbon dioxide gas was fed constantlyat 1.0 l/min (converted under 20° C.) during manufacturing. Table 5shows its result. The dissolving efficiency was lower than that ofExperiment No. 11.

[0214] (Experiment No. 13)

[0215] This experiment was executed in the same manner as in ExperimentNo. 11 except that carbon dioxide gas was fed constantly at 0.5 l/min(converted under 20° C.) during manufacturing. Table 5 shows its result.Although the dissolving efficiency was high, the carbon dioxide gasconcentration was lower than that of Experiment No. 11.

[0216] (Experiment No. 14)

[0217] This experiment was executed in the same manner as in ExperimentNo. 11 except that carbon dioxide gas was fed constantly at 2.0 l/min(converted under 20°) during manufacturing. Table 5 shows its result.Although a high concentration carbonated spring could be obtained in ashort time, the dissolving efficiency was worsened remarkably. TABLE 5Carbon dioxide gas Dissolving Manufacturing concentration efficiencytime (min) (mg/l) (%) Experiment No. 11 10 1310 79 Experiment No. 12 101300 65 Experiment No. 13 10 1080 98 Experiment No. 14 8 1320 43

[0218] Finally, an example using the manufacturing device for theartificial carbonated spring shown in FIG. 6 will be describedspecifically.

[0219] (Experiment No. 15)

[0220] Hot water at 40° C. was poured into the bath by 10 l and 20 l andthe circulation pump (5 l/min), a hollow yarn module produced with thethree-layered composite hollow yarn membrane (made by Mitsubishi RayonCo., Ltd.) whose membrane area was 0.6 m², a carbon dioxide gascylinder, a carbon dioxide gas flow control valve and a measuring devicefor detecting bubbles with ultrasonic wave were connected in the orderindicated in FIG. 6. The flow rate of carbon dioxide gas was set to 1.5l/min, the maximum value (when water is circulated) of a receptionsignal by the measuring device was set to 4.8 mV and the threshold of adetection signal dispatching was set to 3.1 mV (calculated from thedamping rate 65% which provides 1100 mg/l according to FIG. 7) and then,the circulation pump was operated. When the detection signal wasdispatched, the operation was stopped and the carbon dioxide gasconcentration of the produced artificial carbonated spring was measuredwith an ion electrode type carbon dioxide gas measuring device (made byToa Denpa: IM40).

[0221] As a result, artificial carbonated spring having a target carbondioxide gas concentration of 1100 mg/l shown in Table 6 was obtained.TABLE 6 Setting Measured value of Quantity of hot concentration (ppm)carbon dioxide gas water (1) Damping rate (%) concentration (ppm) 101100 1120  65% 20 1100 1100  65%

[0222] Effect of the Invention

[0223] According to the carbonated spring manufacturing device of thepresent invention, which comprises a carbon dioxide gas dissolver and acirculation pump, water in a bath is circulated by the circulation pumpthrough the carbon dioxide gas dissolver and carbon dioxide gas issupplied into the carbon dioxide gas dissolver so as to dissolve carbondioxide gas into water. By raising the carbon dioxide gas concentrationin water gradually, carbonated spring having a high concentration ismanufactured. By retarding the supply velocity of the carbon dioxide gasin the latter half period as compared with the former half period of themanufacturing time, high concentration carbonated spring can be obtainedeffectively.

[0224] According to the carbonated spring manufacturing method of thepresent invention, carbon dioxide gas supplied from a carbon dioxide gascylinder is controlled in terms of the gas flow rate to allow it to flowinto the dissolver and dissolved into hot water. Consequently, acarbonated spring manufacturing method capable of obtaining anunchanging carbonic acid concentration can be provided.

[0225] According to the carbon dioxide gas adding membrane module of thepresent invention, because the carbon dioxide gas permeating amount andvapor permeating amount under a predetermined temperature are set in apredetermined range, carbon dioxide gas can be added into water evenwhen it is fed to hot water. Particularly, because the quantity of vaporpermeating the membrane is small and drain is unlikely to be depositedon the gas side, the frequency of drain discharges and the quantity ofcarbon dioxide to be discharged into the atmosphere at the time of draindischarge can be reduced. Further, because carbon dioxide gas addedwater can be obtained at a high efficiency in a long period, this modulecan be applied widely to applications for adding carbon dioxide gas tolow temperature water, normal temperature water and high temperaturewater.

[0226] Further, because the membrane density of the membrane module isset in a range of 2000 to 7000 m²/m³, drain can be discharged smoothlywhile maintaining the dissolving efficiency of carbon dioxide gas high.When carbon dioxide gas is dissolved after water is heated to 30° C. to50° C. preliminarily, carbon dioxide gas can be dissolved effectively.

1. A device for manufacturing a gas dissolved solution for carbonatedspring, the device manufacturing the carbonated spring and comprising: amembrane module which dissolves carbon dioxide gas into hot waterthrough a membrane; means for supplying hot water to the membranemodule; and means for supplying carbon dioxide gas to the membranemodule, wherein a flow control valve which maintains a flow rate ofcarbon dioxide gas constant and is not affected by a secondary pressureis provided between the means for supplying the carbon dioxide gas andthe membrane module.
 2. The device for manufacturing a gas dissolvedsolution according to claim 1, wherein the flow control valve is a massflow rate type flow control valve.
 3. The device for manufacturing a gasdissolved solution according to claim 1 or 2, wherein a flow meter isprovided between the flow control valve and the means for supplyingcarbon dioxide gas.
 4. The device for manufacturing a gas dissolvedsolution according to any one of claims 1 to 3, wherein a pressurecontrol valve for maintaining gas pressure constant is provided betweenthe means for supplying carbon dioxide gas and the flow control valve.5. The device for manufacturing a gas dissolved solution according toany one of claims 1 to 4, wherein the membrane is hollow yarn.
 6. Thedevice for manufacturing a gas dissolved solution according to claim 5,wherein the hollow yarn membrane is a three-layered composite hollowyarn membrane in which both sides of a thin nonporous gas permeatinglayer are sandwiched by porous layers.
 7. A method for manufacturing agas dissolved solution, wherein, when carbonated spring is manufacturedby dissolving carbon dioxide gas into hot water through a membrane, thecarbon dioxide gas flow rate is controlled to be constant.
 8. The methodfor manufacturing a gas dissolved solution according to claim 7, whereina carbon dioxide gas flow rate is controlled to be constant by a flowcontrol valve.
 9. The method for manufacturing a gas dissolved solutionaccording to claim 8, wherein the flow control valve is a mass flow ratetype flow control valve.
 10. The method for manufacturing a gasdissolved solution according to any one of claims 7 to 9, wherein ahollow yarn membrane is used for the membrane.
 11. The method formanufacturing a gas dissolved solution according to claim 10, whereinthe hollow yarn membrane is a three-layered composite hollow yarnmembrane in which both sides of a thin nonporous gas permeating layerare sandwiched by porous layers.
 12. The method for manufacturing a gasdissolved solution according to any one of claims 7 to 11, wherein, whenhot water in a water bath is circulated by a circulation pump through amembrane module while carbon dioxide gas is supplied to the membranemodule so as to dissolve carbon dioxide gas in the hot water, the ratiobetween the flow rate of the circulation pump and the flow rate ofcarbon dioxide gas is in a range of 2 to
 20. 13. A device formanufacturing a gas dissolved solution for carbonated spring,comprising: a carbon dioxide gas supply port; a carbon dioxide gasdissolver which communicates with the carbon dioxide gas supply port; awater bath; a circulation pump for feeding water in the water bath intothe carbon dioxide gas dissolver and returning into the water bath; andcarbon dioxide gas supply control means for changing the carbon dioxidegas supply velocity during dissolving of carbon dioxide gas.
 14. Thedevice for manufacturing a gas dissolved solution according to claim 13,wherein the carbon dioxide gas dissolver is a membrane module.
 15. Thedevice for manufacturing a gas dissolved solution according to claim 14,wherein the membrane module includes hollow yarn.
 16. The device formanufacturing a gas dissolved solution according to claim 15, whereinthe hollow yarn is composed of a three-layered composite hollow yarnmembrane in which a porous layer is disposed on the front and rearsurfaces of a thin nonporous gas permeating layer.
 17. The device formanufacturing a gas dissolved solution according to claim 13, whereinthe carbon dioxide gas dissolver is a static mixer.
 18. The device formanufacturing a gas dissolved solution according to any one of claims 13to 17, wherein plural carbon dioxide gas supply velocity control meanscapable of setting the carbon gas supply velocities to different levelsare provided in parallel and gas velocity changeover means for thecarbon gas supply velocity is provided.
 19. The device for manufacturinga gas dissolved solution according to claim 18, wherein the gas velocitychangeover means is an electromagnetic valve.
 20. The device formanufacturing a gas dissolved solution according to any one of claims 13to 19, wherein the carbon dioxide gas supply velocity control means is aflow control valve.
 21. The device for manufacturing a gas dissolvedsolution according to claim 20, wherein the flow control valve is a massflow rate type flow control valve.
 22. A method for manufacturing a gasdissolved solution for carbonated spring, wherein, when water in a waterbath is circulated by a circulation pump through a carbon dioxide gasdissolver while carbon dioxide gas is supplied into the carbon dioxidegas dissolver so as to dissolve carbon dioxide gas into the water bathto raise the carbon dioxide gas concentration of water in the water bathgradually, the carbon dioxide gas supply velocity is retarded in thelatter half period of the carbon dioxide gas dissolving time as comparedwith the former half period thereof.
 23. The method for manufacturing agas dissolved solution according to claim 22, wherein the carbon dioxidegas concentration of water in the water bath after dissolving of carbondioxide gas ends is 1000 mg/l or more.
 24. The method for manufacturinga gas dissolved solution according to claim 22 or 23, wherein the latterhalf of carbon dioxide gas dissolving time is longer than the formerhalf thereof.
 25. The method for manufacturing a gas dissolved solutionaccording to any one of claims 22 to 24, wherein the carbon dioxide gassupply velocity just before dissolving of carbon dioxide gas ends is 50%or less the supply velocity when dissolving of carbon dioxide gasstarts.
 26. A method for measuring a gas concentration in a gasdissolved solution, comprising: introducing solution and gas into a gasdissolver each by a predetermined flow rate; measuring the quantity ofbubbles existing in a take-out pipe from the gas dissolver; andmeasuring the gas concentration of a gas dissolved solution dischargedfrom the take-out pipe according to the quantity of the bubbles.
 27. Themethod for measuring a gas concentration in a gas dissolved solutionaccording to claim 26, wherein the quantity of the bubbles is computedaccording to the damping rate of ultrasonic wave passing the take-outpipe using an ultrasonic wave transmitter and an ultrasonic wavereceiver disposed across the take-out pipe.
 28. The method for measuringa gas concentration in a gas dissolved solution according to claim 26 or27, wherein the gas concentration is specified according to the quantityof the measured quantity of bubbles using a relational expressionbetween the quantity of bubbles and gas concentration measured under acondition that the solution flow rate and gas flow rate are constant.29. The method for measuring a gas concentration in a gas dissolvedsolution according to any one of claims 26 to 28, wherein the gas iscarbon dioxide gas while the solution is artificial carbonated spring.30. A device for manufacturing a gas dissolved solution, comprising: agas supply source having gas flow rate adjusting means; a gas dissolverin which gas and solution are to be introduced from the gas supplysource; solution flow rate adjusting means for controlling the flow rateof the solution introduced into the gas dissolver to be constant; and atake-out pipe for taking out a solution from the gas dissolver, themanufacturing device further comprising: a measuring device formeasuring the quantity of gas bubbles existing in the take-out pipe; anda control device for computing the gas concentration of the solutionbased on a relational expression between the quantity of bubbles and gasconcentration measured preliminarily under a condition that the solutionflow rate and gas flow rate are constant and a measured value from themeasuring device and controlling the gas flow rate adjusting meansand/or the solution flow rate adjusting means based on the computationresult.
 31. The device for manufacturing a gas dissolved solutionaccording to claim 30, wherein the measuring devices are an ultrasonicwave transmitter and an ultrasonic wave receiver disposed across thetake-out pipe.
 32. The device for manufacturing a gas dissolved solutionaccording to claim 31, wherein the gas dissolver is a static mixer. 33.The device for manufacturing a gas dissolved solution according to claim30 or 31, wherein the gas dissolver is a hollow yarn membrane typedissolver.
 34. The device for manufacturing a gas dissolved solutionaccording to any one of claims 30 to 33, further comprising a storagebath for storing a solution discharged from the take-out pipe, whereinliquid in the storage bath is circulated to the gas dissolver throughthe solution flow rate adjusting means.
 35. The device for manufacturinga gas dissolved solution according to any one of claims 30 to 34,wherein the gas is carbon dioxide gas while the solution is artificialcarbonated spring.
 36. A membrane module for adding carbon dioxide gas,which is composed of a gas permeation membrane in which the carbondioxide gas permeating amount at 25° C. is 1×10⁻³ to 1 m³/m²·hr·0.1 MPaand the vapor permeating amount at 25° C. is 1×10³ g/m²·hr·0.1 MPa orless.
 37. The membrane module according to claim 36, wherein themembrane concentration of the gas permeation membrane in the carbondioxide gas adding module is 2000 to 7000 m²/m³.
 38. The membrane moduleaccording to claim 36 or 37, wherein the gas permeation membrane is ahollow yarn membrane.
 39. The membrane module according to any one ofclaims 36 to 38, wherein the gas permeation membrane is a nonporousmembrane having no Knudsen flow.
 40. The membrane module according toclaim 39, wherein the thickness of the nonporous membrane is 0.1 to 500μm.
 41. A method for dissolving gas for carbonated spring, whereincarbon dioxide gas is dissolved into water heated to 30° C. to 50° C. inadvance using a membrane module for adding carbon dioxide gas accordingto any one of claims 36 to
 40. 42. A device for manufacturing a gasdissolved solution for carbonated spring, wherein, as the membranemodule according to claim 1, the membrane module according to claim 36is used.
 43. A device for manufacturing a gas dissolved solution,wherein, as the membrane module according to claim 14, the membranemodule according to claim 36 is used.
 44. A device for manufacturing agas dissolved solution, wherein, as the gas dissolver according to claim30, the membrane module according to claim 36 is used.